Baghdad, Iraq ? U.S. troops and guerrillas armed with mortars and rocket-propelled grenades battled for hours Friday in the alleyways of Fallujah, killing a Marine and at least five Iraqis, including an ABC News cameraman.

Near Tikrit, four members of the U.S.-trained Iraqi Civil Defense Corps and three suspected rebels died during a raid by Iraqi security forces and U.S. soldiers, the U.S. military said. Twenty-one suspected guerrillas were captured in the raid north of Baghdad.

Altogether, the fighting and the raid killed 13 people Friday.

Footage from Associated Press Television News showed American troops in Fallujah carrying a comrade in a stretcher shortly after an explosion during combat. The U.S. military in Baghdad said one Marine died and several were wounded in the fighting in a city that has resisted American efforts to pacify it since the ouster of Saddam Hussein a year ago.

This week, U.S. Marines took over authority in Fallujah and surrounding areas from the Army’s 82nd Airborne Division. The city on the banks of the Euphrates River sits in the so-called Sunni Triangle, where support for Saddam was strong and rebel attacks on American forces are frequent.

Witnesses said heavy gunfire and explosions erupted when Marines moved into the center of the city. In recent months, American troops have rarely ventured into downtown Fallujah, one of the most dangerous areas in Iraq for the U.S. military.

Throughout the day, the city was largely deserted with shops shuttered and residents staying indoors. U.S. troops blocked a city entrance.