The US State Department has issued a global travel alert to all US citizens following the death of al-Qa'ida leader Osama bin Laden, warning of "enhanced potential" for anti-American violence.

US President Barack Obama confirmed today the world's most wanted terrorist, Osama bin Laden, is dead.

Speaking from the White House the US commander-in-chief said, "I can report to the American people and to the world, that the US has conducted an operation that killed Osama bin Laden.”

Following the announcement the US also put its embassies on alert, warning Americans of al-Qa'ida reprisal attacks.

US military bases around the world have been ordered to raise their threat level.

Mr Obama said the US had been narrowing down bin Laden's whereabouts since receiving breakthrough intelligence in October.

The US president finally ordered a military strike this morning on a compound in Abbottabad, about 65km north of the Pakistani capital Islamabad.

"After a firefight they killed Osama bin Laden and took custody of his body," Mr Obama said.

"The death of bin Laden marks the most significant achievement to date in our nation's efforts to defeat al-Qa'ida."

But Mr Obama said the death of bin Laden would not end the fight against terrorism.

"We must and will remain vigilant at home and abroad," he said.

Mr Obama stressed the US was not at war with Islam and that bin Laden was a mass murdered or Muslim people.

"His demise should be welcomed by all who believe in peace," Mr Obama said.

"Bin Laden had declared war against Pakistan as well and ordered attacks against the Pakistani people.

"They agree that this is a good and historic day for both of our nations."

Bin Laden's body has reportedly been moved to Afghanistan.

Mr Obama said cooperation with Pakistan had helped lead the US to bin Laden.

He said the United States people understood the cost of war, but would not stand by if threatened.

"As a country we will never tolerate our security being threatened nor stand idly by when our people have been killed," he said.

"We will be relentless in defence of our citizens and our friends and allies.

"We will be true to the values that make us who we are.

"And on nights like this one we can say to those families who have lost loved ones to al Qaeda terror, justice has been done."

Pakistani officials also confirmed death of bin Laden, saying his death was the result of "highly sensitive" operation involving Pakistani intelligence operatives.

It has been reported DNA tests confirmed his death.

Citing a senior Pakistani official, The Wall Street Journal said bin Laden was killed in a joint raid in Pakistan's northwestern district of Abbottabad..

The town also is home to a Pakistani military academy. Two American helicopters took part in the operation, the official said. One Pakistani helicopter involved in the raid crashed after it was hit by fire from militants.

Outside the White House, tourists and visitors were heard chanting USA! USA! before Obama made any official announcement.

The Muslim fanatic, 54, is blamed for masterminding the 9/11 terrorist attacks that killed more than 3000 people.

On September 11, 2001, al-Qa'ida terrorists hijacked four commercial passenger jet airliners and intentionally crashed two of them into the Twin Towers of the World Trade Center in New York City, killing everyone on board and many others in the building.

A third hit the Pentagon and the fourth crashed in a field after passengers fought back against the hijackers.

The US has relentlessly pursued its search for bin Laden after he evaded capture during the American-led invasion of Afghanistan.

US armed forces have been hunting the Saudi terror kingpin for years, an effort that was redoubled following the 2001 terror attacks on the World Trade Center in New York and the Pentagon which killed 3000 people.

But bin Laden always managed to evade US armed forces and a massive manhunt, and was most often thought to be hiding out in Pakistan and Afghanistan border areas.

Late last month Bin Laden warned al-Qa'ida would unleash a "nuclear hellstorm" if bin Laden was captured, according to classified documents released by WikiLeaks.

The documents, released by Wikileaks and detailing the interrogation of more than 750 Guantanamo Bay detainees, reveal that the terrorist organisation plotted major chemical and biological attacks on Britain and mass poisonings across the US.

The intelligence assessments, written between 2002 and 2009 by US military intelligence officials, provide a detailed account of the movements of bin Laden, his deputy Ayman al-Zawahiri and other senior al-Qa'ida leaders following the September 11, 2001, terrorist attacks on New York and Washington.

According to documents, a senior al-Qa'ida commander claimed the terrorist group had hidden a nuclear bomb in Europe that would be set off in the event of bin Laden's capture or assassination. Numerous attempts by al-Qa'ida to obtain nuclear materials and uranium were uncovered by interrogators, the paper said.

The threat to unleash a nuclear hellstorm was made by Khalid Shaikh Mohammed, the most senior detainee held at Guantanamo and the confessed mastermind of the 9/11 attacks, who is due to face a military tribunal later this year.