"The Marines, part of the 1st Marine Expeditionary Force, were part of a quick reaction force responding to Marines who were engaged by hostile forces," Centcom said in a statement.

"The vehicle accident occurred prior to arriving at the ambush site," near Al-Hillah, 100 kilometres (60 miles) south of Baghdad on Wednesday.

"Three Marines were also wounded as a result of the ambush.

"All six Marines were immediately evacuated to a nearby military surgical unit," the statement said but gave no further details.

The latest death brings to 55 the number of US troops who have died since President George W. Bush declared the war in Iraq effectively over on May 1, according to an AFP count from US military statements.

Seventeen of those were killed in attacks and the rest in accidents.

WAR.WIRE