Members of an elite Navy Seals team dropped by helicopter to the compound were under orders to kill, not capture bin Laden, who had eluded US forces for 13 years, a senior US security official told Reuters.
"This was a kill operation," the official said, speaking on condition of anonymity.
Many analysts see bin Laden's death as largely symbolic since he was no longer believed to have been issuing operational orders to the many autonomous al-Qaeda affiliates around the world.
Fearful of revenge attacks, the United States swiftly issued security warnings to Americans worldwide.
A top Republican lawmaker briefed by the White House on bin Laden's death said US security agencies were working to prevent any attacks on the United States or its installations overseas.
"This is a key moment because al-Qaeda has to avenge. This is a terrible defeat for them and they have to move as quickly as they can, and it's up to us to stop them," said congressman Peter King.
Bin Laden's death is unlikely to have any impact on the nearly decade-long war in Afghanistan spawned by the September 11 attacks on Washington and New York.
US forces there are facing record violence by a resurgent Taliban, which has vowed to avenge his death.