Al Qaida leader Osama bin Laden has been killed in Pakistan, US President Barack Obama has announced.
As thousands gathered in Washington to celebrate the 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 Obama, announcing the operation in a televised statement in Washington, said the US operation took place on Sunday.
One of the helicopters, which took off from a Pakistani air base in the north of the country, crashed after it was apparently hit by fire from the ground but there was no information on casualties.
The BBC's Syed Shoaib Hasan in Karachi says that US Special Forces and US Marines do have a base relatively close to Abbottabad, the city outside which Osama bin Laden was killed.
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 on Monday and warned of the heightened possibility for anti-American violence after the killing of al Qaida leader bin Laden by American forces.
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.
US officials added they are ensuring bin Laden's body is handled in accordance with Islamic tradition and practice.