Washington - Osama bin Laden was shot in the head as he peered out of a door and then pumped with bullets as he convulsed on the floor, according to a book by a member of the US commando team that killed him.
The Navy Seal team member's version of the al-Qaeda chief's death differs from previous accounts offered by President Barack Obama's administration and will fuel a debate on the handling of state secrets in the wake of the killing.
No Easy Day to be released next week, offers a first eyewitness account of the May 2011 raid, and describes how a Navy Seal sat on bin Laden's body in the cramped Blackhawk helicopter that flew out of Pakistan after the operation.
Previous official accounts said bin Laden had appeared in a doorway and ducked back into his bedroom, leading the US commandos to suspect he might be retrieving a weapon.
But the author, writing under the pseudonym "Mark Owen", said bin Laden was shot in the head by the Seal team when he leaned out of the doorway and was found bleeding from his wound when commandos made their way to his room, according to excerpts cited in media reports and confirmed to AFP by defence officials.
Bin Laden was mortally wounded and twitching on the floor as two women cried over his body. The team pushed aside the women and then fired more shots at the al-Qaeda leader, according to the book.
Release date moved up
We "fired several rounds", the author wrote in the book. "The bullets tore into him, slamming his body into the floor until he was motionless."
The publisher, Penguin Group's Dutton, has moved up the scheduled release date from 11 September to 4 September, as media coverage has fuelled a flood of orders for the book.
The Obama administration had said Bin Laden's body was treated with dignity and given a Muslim burial at sea.
But on the helicopter flight out of Pakistan, a Seal member sat on Bin Laden's chest due to cramped quarters on the chopper, according to the book.
US officials insisted there was no display of disrespect, even if the author's description was accurate.
The commandos had already lost one helicopter in the operation, which crash-landed at the compound, and this made for crowded conditions on the remaining aircraft, said a defence official, who spoke on condition of anonymity.
Special operations forces crammed into helicopters sometimes have to sit on the bodies of their own fallen comrades, the official added.
Top officials are reviewing the book to determine whether the author revealed any classified information or secret tactics, which would violate Pentagon rules and trigger legal action.
"The Department of Defence has a copy of the book and we're taking a look at it," said Pentagon spokesperson Lieutenant Colonel Steve Warren.
The head of Special Operations Command, Admiral William McRaven, warned in a memo dated 23 August that members of the elite force could face criminal prosecution if they revealed information that endangered US troops.
Fox News has revealed what it says is the identity of the author, a former Navy Seal who also took part in the 2009 operation that rescued Captain Richard Phillips from Somali pirates.
Obama administration officials appeared anxious to avoid having to defend an operation they deem a major success, while suggesting the book did not shed any new light on the raid.
"We are not going to rehash the whole thing," said the US defence official.
"We're not going to comment on his account."
Republican activists and lawmakers have accused Obama's aides of spilling secrets about the raid to Hollywood filmmakers and reporters to bolster Obama's political standing, a charge the White House denies.
The author insisted his book had no political motive and was meant to honour the years of intelligence work and training that led up to the raid.
"You know, if these - crazies on either side of the aisle - want to make it political, shame on them. This is a book about September 11th, and it needs to rest on September 11th, not be brought into the political arena, because this - this has nothing to do with politics," he told CBS television's "60 Minutes.
In the book, he credited Obama for endorsing the raid, but said his teammates made sarcastic remarks that the operation would help the president get re-elected.
When one commando joked that the team had ensured Obama's re-election, the author responded: "Well, would you rather not have done this?"