Four prisoners have been shot dead by US guards during a riot at an Iraqi jail, the US military has said.
The US says it holds about 7,000 inmates in prisons across Iraq
The trouble blew up at the Camp Bucca prison in southern Iraq, after a routine search of cells, the US military said in a statement.
The riot "spread to three additional compounds", and lasted 45 minutes before guards opened fire, it said.
An investigation has been launched into both the unrest and the use of force to deal with it, the military added.
Six other prisoners were injured in the unrest at the prison, near the port of Umm Qasr, the military said.
The statement said prisoners were "throwing rocks and fashioning weapons from materials inside their living areas".
"Guards attempted to calm the increasingly volatile situation using verbal warnings and, when that failed, by use of non-lethal force," it said.
"After about 45 minutes of escalating danger, lethal force was used to quell the violence."
Elsewhere in Iraq, three US marines were killed in a roadside bombing south of Baghdad.
The military said the three were conducting a security operation in Babil province when they died. It gave no further details.
An internet warning purportedly posted by the Iraqi wing of al-Qaeda, run by the wanted Jordanian militant leader Abu Musab al-Zarqawi, has vowed to continue its struggle despite Sunday's election, which it dismissed as an "American game".
"We in the al-Qaeda Organisation for Holy War in Iraq will continue the jihad until the banner of Islam flutters over Iraq," it said.