Osama bin Laden has been killed in a helicopter raid on a mansion in Pakistan.
As thousands gathered in Washington to celebrate his death, it was revealed that four helicopters launched the attack in the Bilal area of Abbottabad, about 60 miles north of Pakistani capital Islamabad.
President Barack Obama, announcing the operation in a televised statement in Washington, said the US operation took place yesterday.
One of the helicopters crashed after it was apparently hit by fire from the ground but there was no information on casualties.
The helicopters took off from a Pakistani air base in the north of the country.
Women and children were taken into custody during the raid.
The news that bin Laden was killed close to Islamabad will raise questions about how he managed to evade capture and how long he had been there.
Most US intelligence assessments had placed him along the lawless border between Pakistan and Afghanistan.
The US State Department put US embassies on alert early today and warned of the heightened possibility for anti-American violence after the killing of al Qaida leader bin Laden by American forces.
The department issued a worldwide travel alert shortly after Mr Obama announced bin Laden’s death. The department warned of an “enhanced potential for anti-American violence given recent counterterrorism activity in Pakistan”.
It said: “Given the uncertainty and volatility of the current situation, US citizens in areas where recent events could cause anti-American violence are strongly urged to limit their travel outside of their homes and hotels and avoid mass gatherings and demonstrations.”
The alert said US embassy operations would continue “to the extent possible under the constraints of any evolving security situation”.
It noted that embassies and consulates may temporarily close or suspend public services, depending on conditions.
As news of the death of bin Laden spread, a large crowd gathered in front of the White House to celebrate, chanting “U-S-A, U-S-A” and waving American flags.
After midnight local time, the crowd filled the street in front and spilled into Lafayette Park.
One of those attending, Alex Washofsky, 20, said he came to celebrate even though he has final exams today at George Washington University. He is a member of the Navy Reserve Officer Training Corps.
He said former president George Bush said the US would get bin Laden dead or alive, “and we did it”.
The New York Police Department (NYPD) welcomed the news.
Police commissioner Ray Kelly said bin Laden’s killing is a “welcome milestone” for the friends and families of those who died on September 11 2001, and for those “who remain tenaciously engaged in protecting New York from another attack”.
Mr Kelly issued a message to all police commands reminding them that while there is no information indicating a specific threat to the nation’s biggest city, officers should remain alert following Mr Obama’s announcement.
More than 20 NYPD officers were killed in the September 11 attack on the World Trade Centre.