A team of seven US soldiers and an Iraqi army interpreter was attacked south of Baghdad today, killing five and leaving three missing, the US military said.
The attack, one of the worst against American ground forces since a security crackdown was launched in Baghdad three months ago, took place near the town of Mahmudiya, a rural area that is a stronghold of al Qaeda militants.
US spokesman Lieutenant-Colonel Christopher Garver said it was not immediately clear if the Iraqi army translator was among the dead or missing.
Last June, al Qaeda militants abducted two US soldiers in the same area in an attack in which a third US soldier was killed. Their mutilated and bobby-trapped bodies were found days later.
Following today's attack, US forces set up checkpoints in and around Mahmudiya. Helicopters, unmanned drones and airplanes were taking part in the search for the missing soldiers, the military said.
The attack comes at a time when US President George W Bush is facing increasing pressure from Democrats to set timetables for withdrawing American troops in a war that has killed more than 3,300 US soldiers and tens of thousands of Iraqis since the invasion in 2003.
The Baghdad offensive, seen as a last-ditch attempt to halt Iraq's slide into all-out civil war between majority Shi'ites and Sunni Arabs, has reduced sectarian murders in the capital but has also driven militants outlying areas.