The US military today released post mortem examination findings from the body of Abu Musab al-Zarqawi, apparently proving that that the terror chief was killed by shockwaves from two 500lb bombs dropped on his hideout.

A series of conflicting accounts over how al-Qaeda's leader in Iraq met his death have fuelled rumours that he may have survived the original blast but been beaten and shot by police or soldiers at the scene.

Questions have also been raised over how al-Zarqawi suffered relatively little visible injury compared to associates also in the safe house in Baquba, north of Baghdad, when it was struck by an airstrike on Thursday night.

Colonel Steve Jones, command surgeon for Multinational Forces, told a press conference that al-Zarqawi survived for 52 minutes after the first of the two co-ordinated strikes on the house. He insisted that shockwaves from the bomb eventually caused his internal organs to fail.

“There was extensive blast injury to the lungs. The cause of death was close based primary blast injury of the lung. Blast waves from the two bombs caused tearing, bruisng of the lungs and bleeding,” he said.

“This wound was not immediately fatal. Death occurred as lung function deteriorated and the lungs became progressively unable to absorb oxygen into bloodstream."

Colonel Jones explained that the difference in al-Zarqawi's injuries from those suffered by his spiritual adviser Sheik Abdul Rahman were explained by their relative positions in the house.

He assured reporters that exploding shells sent the majority of shrapnel out along a relatively well defined line of impact, which killed the cleric instantly.

Major General William Caldwell told reporters that US ground troops arrived about 28 minutes after the airstrike and treated al-Zarqawi, who was breathing with difficulty. A medical examiner was quoted as saying that the terror leader had "no evidence of beating or any firearm injuries."

Maj Gen Caldwell said that the first bomb was dropped by an F-16 at 6.12pm on and that US troops arrived at 6.40pm. Iraqi police were already at the scene.

"His pulse was such that he was not going to live. It was very evident that he had extremely massive internal injuries. At 7.04pm on June 7, Zarqawi was dead."

Al-Zarqawi was the country's most prolific and brutal terrorist, responsible for dozens of suicide attacks and execution-style mass killings that pushed Iraq to the brink of civil war.

He is thought personally to have beheaded at least three Western hostages, including Kenneth Bigley, the Liverpool engineer abducted in September 2004 and murdered three weeks later after being made to beg for his life on video.

The death of the terrorist has given a boost to Iraq's new coalition government of national unity and raised some hope that Iraq's Sunni Muslim minority, most heavily involved in the anti-US insurgency, can be brought back into the political process.

The US explanation of al-Zarqawi's death is unlikely to silence his fanatical followers, who are treating his killing as martyrdom.

Al-Qaeda in Iraq named Sheikh Abu Hamza al-Muhajira as the successor to al-Zarqawi today. The terrorist group praised Sheikh al-Muhajirah's "scholarly" learning, and promised that he would pursue the same campaign of suicide bombings and beheadings begun by the dead Jordanian militant.

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