Former President George W. Bush, who was in office at the time of the Sept. 11 attacks and famously said he wanted Osama bin Laden dead or alive, called the death of the al Qaeda leader a "momentous achievement."

President Barack Obama called Bush in Dallas at 9:04 pm central time to inform him that bin Laden was dead and they spoke for four minutes, a Bush spokesman said, Reuters reported.

Osama bin Laden - the longtime leader of al Qaeda - was killed by U.S. forces in a mansion outside the Pakistani capital of Islamabad along with other family members.