The deaths, on the day the elections were held, drew an angry response from the Iraqi interim government which called for the troops to be put on trial if they were found to have used excessive force.
The US authorities said the soldiers had used "lethal force" on the inmates corralled into compounds, surrounded by razor wire, at Camp Bucca after failing to quell rioting. They also admitted that no American soldiers had been seriously injured by stones thrown by the inmates and the disturbance had lasted just 45 minutes before the decision was taken to open fire.
Bakhtiar Amin, Iraq's human rights minister, said he had sent a delegation to the camp to investigate. "If we are convinced there was no justification for the degree of force used then we want them to be tried," he said. "If there is a mistake, then those in charge should be brought to account."
British military officers said that they were "disturbed" by the Americans resorting to live rounds so quickly, but claimed they were in no position to intervene. Camp Bucca, near Umm Qasar, holds 5,300 prisoners - more than Abu Ghraib jail in Baghdad - some of whom have been detained for more than a year without trial.
There have been repeated allegations of abuse at the prison, which had not attracted the publicity generated by the cases at Abu Ghraib. British soldiers have complained that on at least one occasion American soldiers shot prisoners held in cages.
Trouble began during searches of one of the 10 compounds in the prison camp on Sunday, the day of the Iraqi elections, and spread to three other compounds. A US military statement said the violence started after a routine search for contraband. The facility's commander immediately deployed all available guards to the camp in an attempt to control the situation.
"The riot quickly spread to three additional compounds, with detainees throwing rocks and fashioning weapons from materials inside their living areas. Guards attempted to calm the increasingly volatile situation using verbal warnings and non-lethal force," but when that failed after 45 minutes "lethal force was used to quell the violence". The US troops involved were from a recently arrived reserve unit, the 105th Military Police Battalion, based at Buffalo, New York state.
Allegations of abuse at Camp Bucca have been made by detainees and military personnel. One prisoner, Hossam Shaltout, a Canadian citizen and US resident, said inmates were regularly beaten and humiliated - stripped naked and made to simulate sexual acts. In a compensation claim filed by his US lawyer, Mr Shaltout said guards had placed scorpions on his bound body and that Military Police Master Sergeant Lisa Girman had punched him and kneed him in the groin after he went on a hunger strike. Sgt Girman, who was one of four soldiers discharged over allegations they abused prisoners.
w Iraqi militants claimed yesterday to have taken a US soldier hostage and threatened to behead him in 72 hours unless Iraqi prisoners were released. A photo posted on the internet purported to show a US soldier with his hands tied behind his back. However, a US military spokesman, Staff Sergeant Nick Minecci, said: "No units have reported anyone missing." And there were unconfirmed reports last night that the picture of the "soldier" was actually an action figure doll, widely available in the US. A statement by the "Mujahedin Brigades" named the soldier as John Adams.Reuse content