Osama bin Laden was killed by members of an American commando team without clear indications that he posed a threat, according to a new book authored by one former operative of the famed U.S. Navy SEALs.

The book titled No Easy Day provided minute details on the night raid conducted by the elite U.S. Special Forces in the Abbottabad, Pakistan residential compound owned by bin Laden on May 2011.

Reporting from the book by Mark Owen, The Associated Press (AP) said the al Qaida founder was shot in the head by an unidentified member of the raiding unit.

U.S. forces found him in a room at the top floor of the house, apparently peeking in the pitch dark space before making a quick dash inside when he sensed the presence of the soldiers, the book said according to AP.

Mr Owen said he was behind the pointman of the raiding team and quickly followed when the SEALs raced inside bin Laden's quarters, where they found the terror leader sprawled on the floor with a bullet hole visible on the right side his head.

With bin Laden were two crying women, who were immediately pulled out of the room by the raiding team, with one of them positively identifying the operation's target.

Back inside, Mr Owen and another SEALs member checked on bin Laden, whose body was then twitching and finished him off by firing several rounds through his chest, AP said.

The book ran in counter with the official account released by Washington on the incident, which claimed that bin Laden was perceived by members of the raiding as trying to reach for a weapon before he was felled by muffed gunshots.

There were weapons indeed in bin Laden's room, which the New York Times has identified as a Makarov pistol and an AK-47 assault rifle, but they were left untouched when discovered by the SEAL members, according to Mr Owen accounts.

AP said it obtained an advance copy of the book, which Penguin imprint Dutton said will be published Sept 11, hence the report.

Dutton, however, revised its plans and announced that No Easy Day will hit book shelves a week earlier, citing heavy demands.

Earlier, Mr Owen's identity was unmasked with Fox News first reporting that the author is 36-year old Matt Bissonnette, recently retired from the U.S. Navy.

His accounts on the bin Laden raid drew mixed reactions, mostly on national security concerns as the detailed retelling of SEALs' operations may have exposed operational procedures of the crack commando unit.

The book's author, however, told AP that he did not include anything that "that would compromise national security in any way."

The former SEALs operative also clarified that the mission was not designed to assassinate the man tagged as the brains behind the 9/11, noting that they reached bin Laden's chambers some 15 minutes after the raiding team had descended on the compound.

That amount of time would have given bin Laden ample time to prepare for a last ditch stand that would endanger the SEALs members, Mr Owen said.

At any rate, his exploits could prove a windfall as The NY Times reported that No Easy Day now tops the bestselling lists of Amazon and Barnes & Noble.

It likely too that the book would be transformed into a future movie project as New York Post has earlier reported that Steven Spielberg and HBO were interested on the idea.