Al-Qaeda founder and leader Osama Bin Laden has been killed by US forces in Pakistan, President Obama has said.
The al-Qaeda leader was killed in a ground operation outside Islamabad based on US intelligence, the first lead for which emerged last August.
Mr Obama said after “a firefight”, US forces took possession of his body.
Bin Laden was accused of being behind a number of atrocities, including the attacks on New York and Washington on 11 September 2001.
He was top of the US “most wanted” list.
The US has put its embassies around the world on alert, warning Americans of the possibility of al-Qaeda reprisal attacks for Bin Laden’s killing.
Crowds gathered outside the White House in Washington DC, chanting “USA, USA” after the news emerged.
‘Lead last August’
Bin Laden approved the 9/11 attacks in which nearly 3,000 people died, saying later that the results had exceeded his expectations.
He evaded the forces of the US and its allies for almost a decade, despite a $25m bounty on his head.
His death will be seen as a major blow to al-Qaeda but also raise fears of reprisal attacks, correspondents say.
Mr Obama said he had been briefed last August on a possible lead to Osama Bin Laden’s whereabouts.
It led to intelligence that the al-Qaeda leader was hiding in a compound deep within Pakistan.
The president authorised an operation to “get Bin Laden” last week, he said, and on Sunday a small team of US forces undertook the operation in Abbottabad, north of Islamabad.
After a “firefight” Bin Laden was killed and his body taken by US forces, the president said.
Former US President Bill Clinton said in a statement: “This is a profoundly important moment not just for the families of those who lost their lives on 9/11 and in al-Qaeda’s other attacks but for people all over the world who want to build a common future of peace, freedom, and cooperation for our children.”
Mr Clinton’s successor, President George W Bush, described the news as a “momentous achievement”.
“The fight against terror goes on, but tonight America has sent an unmistakable message: No matter how long it takes, justice will be done,” Mr Bush said in a statement.