"There was a hit on an anti-aircraft weapon that was outside the city. We found it and we fired at it. It posed a threat to aircraft in the airspace," said marine spokesman Lieutenant Colonel T.V. Johnson.

"It was an air strike."

The anti-aircraft weapon was most likely "artillery designed to shoot down aircraft almost like a big machine gun mounted on a tripod," Johnson said.

He said he did not think the strike was in a residential area. He refused to identify the type of aircraft.

An AFP correspondent in Fallujah reported hearing eight explosions south of Fallujah late Monday just before midnight. Jets were still flying overhead, he said.

Earlier, insurgents shot down an unmanned aircraft in the rebel enclave of Fallujah, an AFP correspondent witnessed.

The drone, used to survey the city where US forces have seldom tread since an April assault, was paraded through the streets on a pick-up truck.

US marines confirmed a drone crashed around Fallujah, but said they did not know why.

Seven US marines and three Iraqi national guard were killed and several wounded in a car bomb attack Monday morning as they passed near Fallujah.