The military, which said DNA analysis confirmed the identity of the corpse as al-Zarqawi's, revealed that he died nearly one hour after US-led forces dropped two 227kg bombs on his safe house north of Baghdad on Wednesday.
"There was extensive blast injury to the lungs. The cause of death was close space primary blast injury of the lung. Blast waves from the two bombs caused tearing, bruising of the lungs and bleeding," US military doctor Colonel Steve Jones told reporters on Monday.
"This wound was not immediately fatal. Death occurred as lung function deteriorated and the lungs became progressively unable to absorb oxygen into bloodstream," he added.
Jones rejected reports that al-Zarqawi was beaten to death after coalition forces found him alive after the air strike.
"He died of blast injuries and there was no evidence of beating. The injuries to his lungs were not survivable. That is what killed him as there were no firearm injuries visible on his body," Jones said.
A spokesman for US-led forces in Iraq, Major General William Caldwell, gave further details on the timing of al-Zarqawi's death and revealed that DNA analysis conducted by doctors from outside Iraq had confirmed the identity of his corpse.
"We have the DNA results of Zarqawi and it matches positive," he said.
He said a medic tended to al-Zarqawi after the air strike, ensuring he was breathing as "he lapsed in and out of consciousness".
The medic noticed that al-Zarqawi's breathing was shallow and pulse weak and concluded that his death was imminent, the spokesman said.
Two 227kg bombs destroyed
"At 7:04 pm on 7 June (the coalition medic on duty) realised that al-Zarqawi was dead. This is approximately 24 minutes after the coalition forces arrived or approximately 52 minutes after the first strike on the safe house," he said.
He said that the findings of the autopsy confirmed the initial conclusion that al-Zarqawi was in an enclosed room at the time of the air strikes.
Meanwhile, a doctor who carried out the autopsy told the news conference from the United States that the autopsies on al-Zarqawi and his spiritual advisor Sheikh Abdel Rahman, who was also killed in the strike along with four others, lasted for "two-and-half to three hours each."
Caldwell said the wounds of the two men suggested that Rahman "was close to the detonation of the bombs. I believe Rahman was hit against a wall as there were severe head injuries. He was more exposed to blast waves than Zarqawi."
Meanwhile, al-Qaeda in Iraq has appointed a person named Shaikh Abu Hamza al-Muhajer to succeed al-Zarqawi, according to an internet message posted on Monday.
"The shura (consultative) council and Al-Qaeda in the Land of Two Rivers have both agreed to appoint Shaikh Abu Hamza al-Muhajer to succeed Abu Musab al-Zarqawi in the leadership of the organisation," said the statement on the al-Hesba website, where al-Qaeda's official statements usually appear.
Its authenticity could not be independently verified.
"Sheikh Abu Hamza is a pious brother with a jihadi track record and a solid scholarly background. We ask God to bless him and to help him finish what Sheikh Abu Musab has started," the statement added.
His nationality was not given, but the word "muhajer" means immigrant in Arabic.