U.S. Marines backed by aircraft fought insurgents in the Iraqi city of Falluja on Thursday, six weeks after launching a major attack that aimed to quell revolt in the city before next month's election. Three Marines were killed in the area, a spokesman said, describing a battle for a building which was destroyed by air power after guerrillas had tried to set up a strongpoint in it. "At approximately 10:30 (0730 GMT) this morning in northern Falluja, elements of 1st Marine Division were engaged with anti-Iraqi forces," Lieutenant Lyle Gilbert said, referring to militant groups that have been fighting in Falluja for weeks. "At 11, all Marines were cleared of the building from which the AIF were fighting. Marine aircraft destroyed the building, which had been or was being fortified by insurgents." He added that three Marines were killed in action in Anbar province, which includes Falluja, but in keeping with standard practice he gave no further details of where they died. The first few of Falluja's more than 250,000 residents were escorted back to the city on Thursday, but it remains a ghost town and it is not clear when services will be ready and buildings repaired sufficiently for most people to go home. --SP 2138 Local Time 1838 GMT