Aaron Alexis, 34, of Fort Worth, Texas, died in a gun battle with police during the rampage at Washington Navy Yard.

Eight others were injured in the attack, which began at around 8:20 local time (12:20 GMT) on Monday.

US President Barack Obama ordered flags be lowered to half mast at the White House and on Capitol Hill.

He said he mourned "yet another mass shooting" and condemned the "cowardly act".

No motive is known for the attack, whose dozen victims ranged in age from 46 to 73, said the authorities.

Police initially responded to reports of two other armed suspects, but after exhaustive searches Washington Police Chief Cathy Lanier said on Monday night they were all but certain that Alexis was the only gunman.

Witnesses said the suspect sprayed bullets in a hallway and fired from a balcony down on to workers in an atrium at the heavily secured installation in the US capital.

He was reportedly armed with an AR-15 semi-automatic rifle, a shotgun and a handgun that he took from a police officer at the scene.

Chief Lanier told reporters that the attacker "was engaged in shooting with police officers" when he died. "There is no question he would have kept shooting," she added.

Valerie Parlave of the FBI said that the suspect, who was employed by a subcontractor that was working on a US Navy intranet network, had a valid pass to enter Washington Navy Yard.

Alexis was formerly a petty officer 3rd class who served full-time in the naval reserve from 2007-11, said the US Navy.

It was not immediately clear why he left the military, but unnamed military officers told US media there had been a series of misconduct issues during his service.

According to media reports, Alexis was a Buddhist convert who had had two previous gun-related brushes with the law.

In 2004 he was arrested in Seattle for shooting a construction worker's car tyres, in what he described as an enraged "black-out".

And he was questioned by Fort Worth police in 2010 after firing his gun through the floor of an upstairs apartment. He said it was an accidental discharge.

In addition to those killed in Monday's rampage, one police officer was shot in the legs, a female civilian was shot in the head and hand, and another woman was treated for a shoulder wound.

All three were expected to recover, said Washington Hospital Center officials.

Five others required medical treatment, mostly for minor injuries, said Washington DC Mayor Vincent Gray.

As news of the shooting emerged, emergency vehicles and police surrounded the complex, while helicopters hovered overhead.

The US Senate buildings and six nearby schools were temporarily placed on lockdown as a precaution, while flight departures were briefly suspended at Reagan National Airport.

Patricia Ward, who works at Washington Navy Yard, said she had heard three shots, a pause, and then four more.

"Everybody was panicking and trying to decide which way to get out," she told reporters.

The Washington Nationals baseball team called off their game against the Atlanta Braves on Monday night at Nationals Park, not far from Navy Yard.

Monday's mass shooting occurred at a building that serves as the headquarters for the Naval Sea Systems Command, which builds and maintains ships and submarines for the Navy.

Washington Navy Yard is the US Navy's oldest shore installation, first opened in the early 19th Century, according to the Navy.

They said that the unprecedented salvage effort "reached degree zero [vertical], which was our target".

In the operation that took all of Monday and most of the night, they used cables and metal boxes filled with water to roll the ship onto a platform.

The Costa Concordia capsized in January 2012, killing 32 people.

The bodies of two of the victims of the disaster, by the island of Giglio, have never been found. There are hopes that they may be located during the operation.

The ship was declared completely upright shortly after 04:00 local time (02:00 GMT) on Tuesday.

Franco Gabrielli, the head of Italy's Civil Protection Authority, said the vessel was now sitting on a platform built on the sea bed.

"A perfect operation, I must say," said Franco Porcellacchia, leader of the technical team for Costa Cruise, the owner of the ship.

He added that no environmental spill was detected so far.

"I think the whole team is proud of what they achieved because a lot of people didn't think it could be done," said salvage master Nick Sloane - but he added "it's not over yet".

When the vessel was finally righted in the early hours of Tuesday morning, there was a giant cheer from people gathered at Giglio harbour, says the BBC's Matthew Price, and rescue workers have been out celebrating with coffees.

As daylight broke, the now-upright, brown hulk of the ship was visible - its hull muddy and crushed from 20 months spent submerged on its side.

The man, Ji Zhongxing, said he had been paralysed after being beaten by security agents in China in 2005.

No one was killed in the blast, although Mr Ji suffered injuries and was taken to hospital.

If found guilty, he could face three to 10 years in jail for endangering public safety, state media report.

Photos in state media showed Mr Ji giving evidence from a hospital bed to the court.

According to the verified microblog feed of the Beijing court, Mr Ji said he did not deliberately detonate the home-made device and that he regretted his actions.

His lawyer, Liu Xiaoyuan, said that Mr Ji "took out the explosives at the airport to raise awareness about his plight", and "detonated the explosives by mistake" when he was putting them down.

"This is a case of an explosion caused by negligence," he wrote on his microblog.

Prosecutors said that Mr Ji had endangered public safety and should be held criminally responsible for the explosion, news agency China News Service reported.

The 34-year-old from central Shandong province had been petitioning the authorities over his lower limb paralysis, which he said was caused by a beating from several security officers in Dongguan, south China's Guangdong Province, in 2005.

Mr Ji was also apparently dissatisfied with the way his complaints against the authorities had been dealt with.

His case drew widespread sympathy from the Chinese public, the BBC's Martin Patience in Beijing reports.

While an extreme example, it exposed the immense frustrations many feel in China when trying to seek justice, our correspondent adds.

There were reports of petitioners gathering outside the court, expressing support for Mr Ji and asking for their grievances to be considered.

There was also considerable sympathy for Mr Ji on China's microblogs.

Sina Weibo user nymfj wrote: "I hope he is pardoned", while user Let Go of Your Arrogance asked: "Has anyone investigated the case where Ji Zhongxing was beaten?"

Sina Weibo user Old Yip's Comments wrote: "Ji Zhongxing is a man pushed to the brink by Chinese society. From media reports, you can see that he did not want to harm anyone with his 'explosion', he only wanted to gain attention for his plight. I recommend he is given a reprieve. At the same time, the Guangdong government must give him compensation, and support him for the rest of his life."

However, some users argued that Mr Ji should be punished.

"These cases show that terrorism must be opposed everywhere... it must all be dealt with in accordance to the law," user Zhang Yiwu wrote.

According to China Central Television, Dumex allegedly paid doctors and nurses in the northern city of Tianjin to promote its baby formula products.

The report, which cited an unidentified former sales manager, comes amid an anti-corruption drive by Beijing.

Dumex said it was "extremely shocked" by the allegations.

"Dumex Baby Food Co strictly adheres to Chinese laws and regulations," a company spokeswoman said in a statement.

The latest allegations against Danone come amid a government-led crackdown on corruption in its $350bn (£220bn) healthcare market.

Some inquiries have targeted foreign firms, including British pharmaceutical giant GlaxoSmithKline, which is being investigated for allegedly using inducements to promote the sale of its medicines.

In the CCTV report, Danone's Dumex brand is accused of giving "sponsorship fees" or payments of up to 10,000 yuan ($1,632) to hospital staff.

The French food giant has faced numerous problems in China this year.

Danone cut prices for its infant milk formula products by as much as 20% after China's top economic planning body fined it in August for price-fixing.

The firm also had to issue a precautionary recall of its milk formula products last month after one of its suppliers, Fonterra, said some items may have been contaminated.

China is an important market for companies such as Danone, which is the country's third-largest baby formula provider.

Danone's baby nutrition unit also makes more than 20% of its overall sales from China.

Demand for foreign brands has surged in China, after tainted milk scandals in recent years led to a distrust of local producers.

According to some estimates, foreign brands now account for about half of all infant milk sales in China.

But in a TV address Mr Hollande said: "The military option must remain; otherwise there will be no pressure."

Mr Hollande said a vote on a new UN Security Council resolution on Syria could be agreed by the end of the week.

On Monday he will meet US Secretary of State John Kerry to discuss the issue.

The president said sanctions will be enforced to coerce Syria into dismantling or handing over its chemical weapons if Damascus fails to comply.

"It is necessary to include the threat of sanctions if the agreement and the aims of the Security Council resolution aren't carried out,'' he said.

"But the next step has to be finding a political solution to the Syrian crisis."

On Monday Mr Hollande and his Foreign Minister Laurent Fabius will meet Mr Kerry and British Foreign Secretary William Hague to discuss the wording of the new draft resolution.

The BBC's Christian Fraser in Paris says that France takes a hawkish position on Syria - and a majority of French people think it is too hawkish.

But the government has made a commitment to the Syrian coalition and it is worried that the US-Russia agreement will strengthen the position of President President Bashar al-Assad.

Mr Hollande said that there is no place for President Assad in a future Syria - "not him and not the jihadists".

Our correspondent says that the president's refusal to rule out airstrikes - which are still seemingly still on the table - was tough talk.

But it is not yet clear whether his views will be reflected in the UN resolution once it is finally approved.

President Obama on Sunday also welcomed the agreement as a "foundation" that could eventually lead to a political settlement of the Syrian civil war that has killed tens of thousands of people over the last two years.

He said that the US was in a "better position" to prevent President Assad from using poison gas again because of the deal hammered out by Mr Kerry and Sergey Lavrov, the Russian foreign minister.

After being first drafted in Paris, the UN resolution will be taken to Moscow where it will be validated by President Vladimir Putin.

Russia and China have consistently blocked resolutions at the UN Security Council designed to introduce sanctions against President Assad.

On Sunday a Syrian government minister said that the deal was a "victory" that averts war.

The framework document says Syria must provide full details of its chemical weapons stockpile within a week - with the arsenal to be eliminated by mid-2014.

If Syria fails to comply, the deal could be enforced by a UN resolution with the use of force as a last resort.

The US had threatened to attack Syria which it blames for a chemical attack in August which killed hundreds.

President Assad's government denies the allegations and has accused the rebels of carrying out the attack.

The UN's chief chemical weapons inspector has handed in his team's report into the incident to Secretary-General Ban Ki-moon.

UN spokesman Martin Nesirky said that the secretary-general will brief a closed session of the Security Council on its contents on Monday morning and will also brief the 193-member General Assembly later on in the day.

Syria recently agreed to join the global Chemical Weapons Convention, and the UN said it would come under the treaty from 14 October.

The framework deal was announced on Saturday after three days of talks in Geneva between Mr Lavrov and Mr Kerry.

"We welcome the agreement," Syrian Reconciliation Minister Ali Haidar told Russian news agency Ria Novosti, giving his country's first reaction.

"It's a victory for Syria achieved thanks to our Russian friends."

However the timetable for the process is described by analysts as extremely ambitious.

It envisages Syria providing a full inventory of its chemical weapons within one week, all production equipment being destroyed by November, and all weapons being removed from Syria or destroyed by mid-2014.

Mr Kerry and Mr Lavrov said that the UN resolution could be sought under Chapter VII of the UN charter, which allows for the use of force.

But throughout the Russian foreign minister has insisted that force should remain a last-ditch option.

Russia and the US have agreed on an assessment that the Syrian government possesses 1,000 tonnes of chemical agents and precursors, according to a US official.

The US believes the materials are located in 45 sites, all in government hands, half of which have useable quantities of chemical agents.

But it is thought that Russia does not agree on the number of sites, nor that they are all under the government's control.

On Sunday the Syrian National Coalition, the main umbrella opposition group, demanded in a statement that the ban on chemical weapons be extended to the Syrian government's use of ballistic missiles and air power against civilian population centres.

Fighting continued inside Syria on Sunday, with heavy shelling reported by government forces on suburbs of Damascus, where fierce fighting has been taking place for several days.

More than 100,000 people have died since the uprising against President Assad began in 2011.

Millions of Syrians have fled the country, mostly to neighbouring nations and millions more have been internally displaced within Syria.

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.

The attack on Lieutenant Negar - known only by her surname - comes after her female predecessor was killed.

A spokesman for the governor of Helmand said that Lt Negar was shot on Sunday near the police headquarters in the provincial capital, Lashkar Gar.

Lt Negar was rushed to hospital and is expected to survive.

Afghanistan's Independent Human Rights Commission says violence against women has increased sharply over the last two years, and donor nations have expressed fears that advances in women's rights could be at risk when Nato-led troops withdraw next year.

Lt Negar was shot by a gunman on a motorbike, officials say.

Helmand Provincial governor's spokesman Omar Zawak told the AP news agency that the 38-year-old suffered a bullet wound to the neck.

He said that a medical team is trying to prevent her from being paralysed as a result of the injury.

Lt Negar served as a sub-inspector in the police criminal investigation department in Helmand.

She took over from Islam Bibi, a well-known police officer who was shot dead in July by unknown gunmen as she headed to work on her motorbike.

The commander of 32 female police officers, Lt Bibi, 37, was known as a role model for other women in the conservative province.

Several prominent Afghan women have been attacked or kidnapped in recent months.

Earlier this month the Taliban released a female member of parliament who they had held hostage for a month.

In August, insurgents ambushed the convoy of a female Afghan senator, seriously wounding her and killing her nine-year-old daughter.

In 2008 gunmen in Kandahar killed Lt-Col Malalai Kakar, the country's most prominent policewoman and head of Kandahar's department of crimes against women.