A raft of reforms was promised by Portugal's leaders in return for its May 2011 bailout.

The visit from the so-called troika will determine whether the country receives its next instalment of bailout funds.

It is expected to meet the criteria.

The visit was originally expected to take place in July of this year, but was postponed following a political crisis.

There are fears that Portugal's economy remains volatile, and borrowing costs have climbed again in recent months.

The yield on a benchmark 10-year Portuguese government bond soared above the 7% barrier earlier this summer. That is the level at which other European countries have sought a bailout.

However, while unemployment in Portugal is amongst the highest in the eurozone, especially amongst the young, the country reported growth of 1.1% for the second quarter of 2013, after a boost to its export market.

Portugal received 78bn euros ($102bn; £67bn) in May 2011, in return it began a tough austerity programme.

The Portuguese government says it is on track to emerge from the bailout programme in June 2014.

Referring to the official paperwork needed to join the market, thecompany tweeted: "We've confidentially submitted an S-1 to the SEC for a planned [initial public offering]."

Investors value Twitter, founded in 2006 by Jack Dorsey, Biz Stone and Evan Williams, at more than $10bn (£6.3bn).

Twitter gave no further details as to the timing or price of the offering.

The microblogging service is on track to post $583m in revenue in 2013, according to advertising consultancy eMarketer, up from $288m in 2012.

Most of Twitter's funding comes from advertising, with companies paying for "promoted tweets" that appear in users' Twitter feeds.

Advertisers are keen to target Twitter's 200 million active users, who send more than 500 million tweets a day.

But some analysts believe the risk for Twitter post-flotation is that if the drive for greater advertising revenue leads to increased numbers of adverts in and around the site, they could become intrusive and unpopular with users.

"There's a few issues [such as] how many revenue streams can be developed beyond just advertising, the impact of more people accessing the service via smartphones," said Colin Gillis, a New York-based technology specialist at BGC Partners.

Nearly two-thirds of users access Twitter via mobile devices that have traditionally been difficult for advertisers to reach.

This is one reason why Twitter has acquired MoPub, a mobile-focused advertising exchange, for a reported $350m.

"Twitter was more or less a mobile-first platform from the start and so the company built its experience to work relatively well across devices," Clark Fredriksen of eMarketer told the BBC.

"Ultimately, they did a good job of monetising their mobile user base."

"Twitter is one of the last of the major developed social networks to file [for an initial public offering or IPO] - we've already had Facebook and LinkedIn," said Mr Gillis.

Facebook listed on the stock market in May last year. Although it initially created excitement among investors, its share price performed poorly, before recovering this summer.

The timing of the IPO is likely to be related to renewed activity in stock market flotations. There have been 131 IPOs priced so far in 2013, according to IPO tracking firm Renaissance Capital - a 44% increase on the same period last year.

Activity is climbing back towards the pre-financial crisis levels of 2007, says Renaissance.

Andrew Frank, social media expert at technology research company Gartner, said: "[The IPO] gives its investors a way to get some of the money back that they put into the company at the beginning.

"It gives the employees a similar kind of event to reward them for the success they've had so far. And it gives Twitter itself extra funds to invest in new projects and innovation."

Mr Gillis said it was impossible to say how great the demand for Twitter shares would be until the company released a valuation.

Analysts say Twitter must continue to innovate under the scrutiny of public ownership.

"One of the things they will have to focus on is making sure that they keep their users very actively engaged," Nate Elliott, an analyst at the tech consultancy Forrester, told the BBC.

"One of the things Facebook has done very successfully over the past year-and-a-half has been to show that not only is the number of users growing, but that those users are becoming more active."

Twitter's tweet announcing its filing immediately went viral - it was re-tweeted more than 8,000 times within an hour of its posting.

For many users, it seemed apt that the company would use its own platform to announce the news.

"Naturally Twitter announces its IPO via Twitter. What other way?" oneread.

Twitter later sent a follow-up tweet, which read simply: "Now, back to work."

Once a company has filed paperwork with US regulators for a planned IPO, it enters a so-called "quiet period" when it is not allowed to speak to the media.

According to the Securities and Exchange Commission's website, a company can file a confidential prospectus for a public share sale if it is classified as an "emerging growth company" with revenue of less than $1bn.

Sales were up by a seasonally adjusted 0.2%, as US consumers bought fewer items of clothing, sporting goods and building materials.

Economists had expected sales to rise by 0.4%.

Sales of cars rose by 0.9% last month according to the Commerce Department, having dropped 0.5% in July.

Chris Williamson, chief economist at researchers Markit, said the figures supported the expectation that US economic growth will have slowed slightly for the third quarter of the year.

"The message from the various official data that are available is therefore that the economy continued to grow in the third quarter, but that growth is likely to have slipped from the 2.5% annualised pace seen in the second quarter."

However, he added that the overall picture is far from negative.

"Sales have nevertheless now risen in 13 of the past 14 months, the exception being last March, indicating that shoppers have not been deterred from spending by issues such as the payroll tax rise at the start of the year and worries about the fiscal cliff, as many had feared.

Mr Williamson and many other economists still anticipate that the Federal Reserve will announce it is starting to reduce its $85bn a month economic stimulus at its next meeting.

Paul Dales, Senior US Economist at Capital Economics agrees. He said the retail figures, "may support a tapering of QE3 at next week's Fed meeting".

In a separate survey, the Labor Department said that US producer prices rose by 0.3% in August. They had been flat in July.

Where some see dross, others spy gold. Case in point: BRICs.

BRICs — primarily Brazil, Russia, India and China — comprise some of the largest and most-developed global emerging markets, not fared well overall this year. But they are once again being considered by investors as they take a closer look at some battered, and possibly bargain-priced, stocks.

Overall, many investors have been fleeing emerging markets. For the first seven months of the year, emerging market equity funds had a net outflow of $4.5 billion, as global investors scurried back to the US and Europe, lured by the idea that US interest rates could rise — a boon to investment returns — if the Federal Reserve winds down its long-running stimulus program, as widely expected.

But the decline among emerging markets stocks may be leaving some golden buying opportunities, say some experts, especially among the BRICs. Those powerhouse economies, including the core four BRIC countries, have strong fundamentals that can insulate them from some of the broader volatility. Those fundamentals include a large and expanding middle class and increasingly sophisticated, acquisition-minded companies.

They also have strong gross domestic production (GDP), the measure of the value of goods and services produced within the country’s borders.  Overall, measured by purchasing-price-parity adjusted GDP, emerging markets will create $1.6 trillion more goods and services than advanced markets in 2013, according to the International Monetary Fund.

“Cheap”

A recent JP Morgan Asset Management emerging market research report noted that BRIC stocks currently look quite “cheap,” as country valuations hover near the bottom end of historical valuation ranges. All four BRIC countries will have higher GDP growth than the US this year, according to JP Morgan.

China and Russia have relatively low debt, 31% and 12%, respectively. And China’s ample international reserves total nearly $3.5 trillion. Both countries’ GDPs are also growing: China’s growth will hit 8% this year, Russia’s 3.4%.

Though there’s no sign of a comeback yet — for the first seven months of this year, the MSCI BRIC Index has plummeted 11.21% — some investors and big emerging market mutual funds, like ones run by T Rowe Price, are bargain hunting.

“We accept some risk in short-term pain,” said Todd Henry, emerging market equity portfolio specialist at Maryland-based T Rowe Price. “But opportunity is there in growth.”

BRIC stocks make up nearly 50% of The T Rowe Price Emerging Markets Stock Fund’s $7.2 billion in assets. The fund is adding to its BRIC holdings, especially the Russian and Indian stock allocations.

Chinese stocks also don’t look expensive right now, Henry said. In late August, the MSCI China Index price-to-earnings ratio (P/E) — a measure of how expensive a stock is — was only 9.75, versus 11.90 for emerging markets. Currently, the fund favours environmental companies such as wind producer China Longyuan Power Group Corp Ltd and gas company Beijing Enterprises.

Despite India’s plummeting rupee, the country is also high on some investors emerging market stock lists.

“India is becoming a huge buying opportunity,” said Peter Kohli, president of Pennsylvania-based DMS Funds. “The stock market is just taking a breather, but it will come back again.”

The reason, he added, is that India has about 10 years of above-average growth left, partly driven by a huge, acquisition-minded middle class. Indian multinational companies such as Tata Group, Wipro Ltd and Mahindra & Mahindra Ltd will have strong earnings, he said. A depreciated rupee means these companies are now on sale for emerging market investors, he added.

Who should invest?

Bedevilled by wild swings, emerging markets are typically best as part of well-diversified portfolios, or for value-hungry investors with reasonably long investment horizons. The small sizes of most emerging market economies mean they are vulnerable to the vagaries of global investors.

“In the past, these huge investor inflows have helped prop up countries like Thailand and Vietnam,” said Jonathan Galaviz, a managing director at the Nevada-based strategy and research consultancy Galaviz & Co. “For this reason, economies in Asia have been over-heating for the past five years.”

That is beginning to change. For instance, Thailand’s GDP growth is expected to slow to 4.2% in 2014 from 5.9% this year.

Unlike smaller emerging markets, BRICs benefit from being big, diversified economies with highly liquid markets. Even so, they’re best played by using ETFs, say many experts. There are several BRIC ETFs to choose from, including country-specific ones like Market Vectors Russia ETF or the iShares MSCI India Small-Cap ETF.

Alan Miller, chief investment officer at the London-based investment management firm SCM Private, also prefers ETFs. A contrarian investor, he is eyeballing investments in emerging market BRICs like Russia. One reason: The MSCI Russia Index P/E is only 5. “Yet Russia’s earnings growth isn’t falling off a cliff,” he added.

Some other emerging market experts are looking further afield. Philippe Carre, global head of connectivity for SunGard’s Global Trading Business, says that some Eastern Europe countries, especially Poland and Rumania, are becoming star performers. These post-Soviet countries are seeing their exchanges grow, as more companies are listed.

Yet even Carre isn’t immune to the lures of some of the BRICs. “It’s hard to avoid economic locomotives like China,” he said.

The Environmental Protection Agency (EPA) banned BP last November blaming the firm's "lack of business integrity" after the Deepwater Horizon explosion.

The blast in 2010 killed 11 workers and released an estimated four million barrels of oil into the Gulf of Mexico.

BP says the ban unfairly includes 21 of its subsidiaries that were not connected to the spill.

"We believe that the EPA's action here is inappropriate and unjustified as a matter of law and policy, and we are pursuing our right to seek relief in federal court," said Geoff Morrell, BP's head of US communications.

"At the same time, we remain open to a reasonable settlement with the EPA."

BP is one of the biggest suppliers of fuel to the US government.

The ban has not affected existing contracts but has prevented BP from taking new leases in the Gulf where it drills for oil.

BP is also in a battle over its compensation scheme for businesses affected by the 2010 oil spill.

It says there is a risk that hundreds of millions of dollars in claims payments could be fraudulent.

But last month a US judge rejected BP's request to suspend all payments related to the Gulf Coast oil spill.

The $11bn (£7bn) deal, which would form the world's largest airline, was backed by a federal judge in March and has been approved by the European Union.

The complaint says customers would see a price rise as the merger would "substantially lessen competition" in the domestic market.

US Airways boss Doug Parker said the company would fight the injunction.

"We are extremely disappointed in this action and believe the DOJ [Department of Justice] is wrong in its assessment," Mr Parker said in a letter to employees.

The District of Columbia and six US states and have joined the legal action: Texas, where American Airlines is headquartered, Arizona, where US Airways is based, Florida, Pennsylvania, Tennessee and Virginia.

American Airlines and US Airways said that in light of the justice department's action they no longer expected the merger to close by the end of 2013, but that they remained "hopeful" litigation would be over by year's end.

Shares in both companies fell, along with the stock prices of other airlines, as news of the anti-trust case hit the markets on Tuesday.

"By challenging this merger, the Department of Justice is saying that the American people deserve better," US Attorney General Eric Holder said in a statement.

"This transaction would result in consumers paying the price - in higher air fares, higher fees and fewer choices."

The lawsuit also cites direct competition between the airlines on nonstop routes worth about $2bn in annual revenues.

In one example, the complaint says the newly merged company would take up 69% percent of flights out of Washington's Reagan National Airport and 63% of nonstop routes out of the airport.

The airlines had previously conceded take-off and landing slots at airports in Philadelphia and London in order to win EU approval last week.

When the deal was announced in February, US Senate Commerce Committee chairman Jay Rockefeller also expressed concern that consumers would lose.

American Airlines has been in bankruptcy protection since November 2011, but US Airways has been profitable in recent years.

'Stake in the heart'

The two combined airlines would have 6,700 daily flights and annual revenue of roughly $40bn.

The justice department complaint argues the two companies do not need to merge to continue to be competitive, and that American Airlines is likely to exit bankruptcy as a "vigorous competitor".

The department also cited American Airlines' purchase two years ago of 460 new planes, said to be the largest such order in industry history.

If the merger continues, there will be only three major US airlines, which the justice department alleges "increasingly prefer tacit coordination over full-throated competition".

Some industry analysts suggest that American Airlines and US Airways' ability to compete without a merger is not as strong as the department argues.

"I'm not sure if long term either of these airlines can be a viable competitor by itself," Ray Neidl, an airline analyst at Nexa Capital, told the BBC.

"It probably will cause prices to go down in the short term as they compete, but I think long term US Airways and American are going to have a hard time competing."

But one opponent of the two firms' consolidation, Charlie Leocha, director of the Consumer Travel Alliance, told Reuters news agency: "This is a stake in the heart of the merger. I don't see this moving forward."

He said there may be "gradual recovery in economic activity in the remaining part of the year and in 2014".

It comes as the ECB once again kept interest rates at a historic low level of 0.5%.

And Mr Draghi has again said rates will remain at low levels for the foreseeable future.

"The Governing Council confirms that it expects the key ECB rates to remain at present or lower levels for an extended period of time," he said.

His statement that rates would stay low is aimed at reassuring markets that the ECB is not ready to follow the US Federal Reserve towards withdrawing or "tapering" emergency stimulus.

The rate decision comes after some positive indicators this week, including a slight drop earlier in the number of people unemployed in the eurozone.

It was the first fall for some 25 months, although the jobless rate remains at 12.1%.

And on Friday, it was revealed that eurozone manufacturing activity grew for the first time in two years in July as factory output increased.

Markit's Eurozone Manufacturing PMI rose to 50.3, from June's 48.8, breaching the 50 threshold for growth for the first time since July 2011.

Inflation in the currency bloc remains steady at 1.6%, below the ECB's goal of 2%.

Mr Mr Draghi said there were still some challenges ahead, as he warned that eurozone countries should not end efforts to reduce government budget deficits.

"The risks surrounding the economic outlook for the euro area continue to be on the downside," he said. "Recent developments in global and financial market conditions and the related uncertainties may have the potential to negatively affect economic conditions.

"Other downside risks include the possibility of weaker-than-expected domestic and global demand and insufficient implementation of structural reforms in euro area countries."

The euro dropped to an intra-day low of $1.3196 after his remarks before moving to $1.3217, down 0.6% on the day.

Chinese banks rapidly expanded credit in the market after the global financial crisis to boost growth

Local governments in China borrowed heavily after the global financial crisis to try to sustain growth rates.

The last audit, published in 2011, showed they had debt of 10.7tn yuan ($1.7tn; £1.1tn) by the end of 2010.

Debt may threaten China's growth, and there are growing fears that local governments may not be able repay.

"In line with a request of the State Council, the National Audit Office (NAO) will organize auditing agencies across the country to carry out an audit of government debt," the national auditor said in a statement on its website.

The NAO said that it had halted all other projects to conduct the audit, but did not give any other details or a timeline for the audit.

A large part of the local government borrowings were taken up after the global financial crisis as Chinese authorities released a 4tn yuan fiscal stimulus.

According to the China Banking Regulatory Commission, local governments took up 80% of total bank lending in China at the end of 2010.

Some of the borrowings were spent on infrastructure projects, such as road and rail - seen as vital to sustain orderly economic development - but some of it also went into property construction.

There have long been fears that the projects may not be financially viable in the long run.

"A lot of the projects that were invested in will not have the kind of returns that they had initially estimated," said Dariusz Kowalczyk, senior economist with Credit Agricole-CIB in Hong Kong.

"That coupled with slowing growth means that the finances of the local governments may not look too good."

'Large and unknown'

At the same time, there have been concerns about the size of total government debt in China, with some arguing that the figures for local government debt have been underestimated.

According to the NAO's last audit, local government debt was around 25% of the China's total gross domestic product (GDP).

But many have said that the levels may be much higher than that.

Mr Kowalczyk said that the concerns about the bad loans in China were serious because "the size of the debt is large and unknown".

However, he added that the audit was a step in the right direction and would be good for the country in the long run as it should help bring out the details on the the size of the problem.

There are also concerns over the way the local government debt has been managed.

Last year, the audit office said that it had uncovered 531bn yuan of irregularities in local government debts.

It said that breaches included "irregular credit guarantees", "irregular collateral" and "fraudulent and underpayment of registered capital".

The Chinese central government has repeatedly stressed the urgent need to guard against financial risks, including the local government debt problem.

In June, Liu Jiayi, auditor general with the NAO, warned at a session of China's top legislature that local governments must improve their debt management in order to handle escalating growth in local debt.

Both sides have agreed a minimum price for the panels, EU Trade Commissioner Karel De Gucht said.

The dispute erupted after the Commission - the EU's executive arm - imposed temporary anti-dumping levies on the imports.

It argued that Chinese firms were undercutting rivals.

China is the world's largest producer of solar panels. Its exports to Europe totalled 21bn euros ($27bn; £18bn) in 2011.

"After weeks of intensive talks, I can announce that I am satisfied with the offer of a price undertaking submitted by China's solar panel exporters," Mr De Gucht said on Saturday.

"This is the amicable solution that both the EU and China were looking for."

He added that the agreement would "lead to a new market equilibrium at sustainable prices".

The anti-dumping case was the biggest ever undertaken by the Commission.

In June, the EU accused China of "dumping" solar panels in Europe - selling them at below cost to steal market share - and then said it would impose import tariffs of up to 47.6% on them.

China said EU farm subsidies had resulted in European countries "dumping" wine on China, and warned it may respond in kind.

Investigating magistrates have decided he should be tried in connection with an alleged prostitution ring at a hotel in Lille.

The former presidential hopeful has admitted attending sex parties there, but says he did not know that some of the women were paid prostitutes.

The case is the last of the sex-related allegations faced by Mr Strauss-Kahn.

A series of lurid claims have been made about the high profile French figure since he was arrested in New York in May 2011 after a hotel maid said he had tried to rape her.

Charges were eventually dropped, and Mr Strauss-Kahn subsequently reached a settlement with the maid, Nafissatou Diallo.

Two other cases against him have also been dismissed.

An allegation of sexual assault in Paris in 2003 was not pursued because it had taken place too long ago.

And in October last year, French prosecutors ended an investigation into allegations of gang rape at a hotel in Washington after the woman who made the claim retracted her evidence.

French prosecutors recommended last month that the Lille allegations - known as the Carlton affair after the hotel where the orgies allegedly took place - should be dropped.

The latest announcement makes clear, however, that the legal difficulties of the disgraced politician are not yet over.

The investigating magistrates are not obliged, in the French legal system, to follow the advice of the prosecutors, and on this occasion they have not.

Mr Strauss-Kahn was originally under investigation for "aggravated pimping as part of an organised gang". He is now facing the slightly less serious charge of "aggravated pimping as part of a group," along with 12 others.

His lawyer told Le Monde that the legal team was "under no illusions" as to the relentlessness shown by the magistrates towards their client.

"This decision is based on an ideological and moral analysis, but certainly not on legal grounds," he said.

"We will demonstrate in the criminal court that it is a total aberration."

Mr Strauss-Kahn, who stepped down as International Monetary Fund leader after his arrest in New York, had looked like a plausible Socialist challenger for last year's presidential elections.

However, the IMF added that the recovery from recession has so far been "tepid".

In its regular assessment of the economy, the IMF said the US still faces "powerful headwinds".

But it noted gains on stock markets and in house prices, and predicted that economic growth should gradually accelerate over the next year.

The IMF said the expiration of the payroll tax cut earlier this year and the impact of government spending cuts (through the so-called sequester) were "weighing significantly on growth this year".

However, further ahead, the IMF sees a slightly brighter picture and expects "economic activity to accelerate to 2.7% next year as the fiscal drag subsides and the negative legacies of the financial crisis wane further".

On unemployment, the IMF predicted that the rate would remain broadly stable this year, "reflecting the pickup in the labour force participation as discouraged workers return to the labour force".

It also expects the rate of unemployment to gradually fall in 2014.

Gradual acceleration

The Federal Reserve's policy of keeping interest rates very low (close to zero) was also seen by the IMF as still being necessary to support the recovery.

Overall, the IMF felt that the improvement in the underlying conditions of the US economy "bodes well for a gradual acceleration of growth".

The IMF's assessment is in stark contrast to one it released early this week on the eurozone, in which it concluded that the economies in several member countries remained weak.