Militant leader Abu Musab al-Zarqawi died from injuries consistent with the results of a bomb blast, US military officials have said.
Pictures of Zarqawi's body were put on display by the US
Questions had arisen over how he had died after the Americans revealed he had still been alive following the bombing of a safe house by US planes.
An autopsy revealed the cause of death was a blast injury to the lungs, but he took nearly an hour to die, they said.
Al-Qaeda in Iraq has named a successor, according to an internet statement.
Abu Hamza al-Muhajir has been appointed to take over as leader following the killing, according to the message on a site reportedly used by Islamist militants.
Observers say little is known about the purported successor.
In other developments:
- The US military in Iraq says its aircraft killed nine people in an attack on a "terrorist cell", but witnesses say the dead are civilians
- US President George W Bush is holding two days of discussions with military officials and diplomats for what his advisers say is a crucial reassessment of the war in Iraq.
Zarqawi and five others were killed after US planes dropped two 500lb (230kg) bombs on Zarqawi's safe house near the city of Baquba on Wednesday.
Giving the first details of Zarqawi's autopsy, US military doctor Steve Jones told reporters DNA analysis had confirmed the corpse was Zarqawi's.
"The cause of death was close based primary blast injury of the lung", he said.
There had been tearing, bruising and bleeding in the lungs, which had not been apparent from an external examination, the US official said.
This wound was not immediately fatal, he added.
"Fatal death occurred as lung function deteriorated and the lungs became progressively unable to absorb oxygen into bloodstream," he said.
Col Jones said the body of the leader of al-Qaeda in Iraq bore "no evidence of beating or any firearm injuries".
An autopsy on the body of Zarqawi's spiritual adviser Sheikh Abd-al-Rahman revealed that he had been killed instantly in the air strike, he added.
Zarqawi had died about 52 minutes after the first bomb hit the site and 24 minutes after US forces arrived at the scene, Major General William Caldwell said.
He said they administered medical help to the mortally wounded Zarqawi.
"At 1904 on 7 June, Zarqawi was dead."
Gen Caldwell said the "scientific facts" provided "irrefutable evidence... to counter speculation, misinformation and propaganda".
"The Iraqi people deserve the facts, to know that the personal threat of Zarqawi was eliminated and the fact that he was treated better in death than he treated others in life," he added.
US military officials have denied widely reported eyewitness allegations suggesting Zarqawi had been beaten by US soldiers before his death.
The US had earlier said Zarqawi did not survive the air strike, which they said came after tip-offs from his organisation.