Two U.S. Marines were killed and three other Marines and a U.S. sailor were also presumed killed in a powerful suicide car bomb attack on a U.S. convoy, a U.S. military official said today. "Two Marines were killed and we presume that the other four troops, who are missing, were killed," the official told Reuters in Washington. A statement released by the U.S. Marines said only that the three missing Marines and a sailor believed to be the U.S. military vehicle attacked in Falluja on Thursday were "currently listed as Duty Status Whereabouts Unknown pending a positive identification." The attack occurred late Thursday in the violent city west of Baghdad that was until recently a stronghold of the insurgency.