An Iraqi civilian was killed by U.S. troops during an ambush in the troubled city of Fallujah (search), the military said Sunday.

It said gunmen attacked a U.S. patrol with automatic weapons and a rocket propelled grenade late Saturday. Soldiers returned fire and killed one of the assailants, while the other fled, said a statement released by the Central Command (search).

None of the U.S. soldiers was injured.

"Pockets of resistance remain in the region between Fallujah and Ramadi and they appear to be coordinated at the local level," it said.

Fallujah, a Sunni Muslim (search) stronghold about 30 miles west of Baghdad, has been the scene of almost constant clashes since U.S. troops shot dead 18 demonstrators and wounded 78 others in two confrontations in April.

More than 1,500 troops from the 3rd Infantry Division were added to the area between Fallujah and the nearby town of Ramadi to prevent unrest and quell the attacks.

Dozens of U.S. troops have been killed or injured in central Iraq since the end of the war nearly two months ago.