U.S. and Iraqi forces are pushing deeper south into the city of Fallujah on the fifth day of a joint offensive to drive out insurgents.

A fierce battle erupted earlier Friday near a mosque in Fallujah's Jolan district, and U.S. Marines went house to house to secure the former rebel stronghold.

American military officials say U.S. and Iraqi forces now control nearly all of Fallujah, but still face pockets of resistance by insurgents trapped in the southern part of the city. Hundreds of insurgents have been killed or captured since the assault began Monday.

Eighteen Americans and five Iraqi troops also have been killed.

In Iraq's third largest city, Mosul, U.S. forces launched airstrikes late Thursday following a rash of street battles and insurgent attacks on police stations.

One American soldier was killed in Mosul on Thursday.