Two Obama administration officials say DNA evidence has proven that Osama bin Laden is dead, with 99.9% confidence.
The officials did not say where or how the testing was done but the test explains why President Barack Obama was confident to announce the death to the world last night.
Earlier, US Secretary of State Hillary Clinton has warned al-Qaida that the killing of bin Laden in Pakistan proves the terrorist network cannot defeat the United States.
Mrs Clinton urged members of the group to abandon violence and rejoin society following bin Laden’s death, which she described as a “milestone” in the war on terrorism.
She stressed that the “battle to stop al-Qaida and its syndicate of terror” is not over, but stressed that the operation to find and kill bin Laden nearly a decade after the 9/11 terror attacks showed the US would never abandon its pursuit of justice.
Mrs Clinton said the US would continue to boost its counter-terrorism cooperation with other nations, including Pakistan.