SAMARRA, Iraq - Sporadic gunfire echoed through this Sunni Muslim stronghold Saturday as U.S. and Iraqi forces battled pockets of resistance a day after the start of what appeared to be the first major push to regain control of a string of cities before elections in January.

More than 100 guerrillas were killed and 37 captured on the first day of the operation Friday, according to an Iraqi official. The military said one American soldier was killed and four were wounded after some 5,000 swept in to seize the city hall, the main mosque and other key sites in Samarra.

The city appeared mostly calm Saturday except for in the center, where American snipers on rooftops fired at anybody appearing in the streets below. Residents in outlying areas emerged from their homes for the first time to survey the damage.

Also Saturday, the military said that a U.S. soldier from Task Force Baghdad was killed by small arms fire. The incident happened late Friday and caused no other casualties, the statement said. No further details were disclosed. The incident is under investigation.

The U.S. military and Iraqi authorities said they controlled some 70 percent of Samarra and only pockets of resistance remained. Many bodies were strewn in the street but could not be collected for fear of the snipers, residents said.

"They are buried in the gardens of their homes," said Ali Abdul-Latif, a 19-year-old high school student.

Saturday was the first official school day after a nationwide holiday, but Abdul-Latif and other students in Samarra stayed home. A 7 p.m. to 7 a.m. curfew was in effect, and water and electricity services were severed.

Also Saturday, a car bomb targeting a U.S. Marine convoy exploded east of Fallujah, another one of the cities that remain beyond U.S. and Iraqi government control. One member of the convoy was injured, said 1st Lt. Lyle Gilbert, a Marine spokesman. He did not disclose the nationality of the victim.

U.S. forces also clashed Saturday with insurgents in the vast Baghdad slum of Sadr City, police and witnesses said.

The fighting came after American warplanes and tanks attacked militants holed up in the neighborhood overnight. A hospital director said 12 Iraqis were killed and 11 were wounded in the earlier strikes. The U.S. military, which maintains casualties are often exaggerated by Iraqi hospital sources, said only one armed insurgent was killed.

Late Friday, a U.S. airstrike flattened two houses in the insurgent-held city of Fallujah, witnesses said. The military said the strike targeted a safe house used by followers of Jordanian terror mastermind Abu Musab al-Zarqawi.

The Americans said they conducted the operation in Samarra, 60 miles north of Baghdad, at the request of the Iraqi government. It wasn't known if the attack marked the launch of major military operations to wrest other areas of the country from insurgents ahead of the elections.

U.S. military officials have signaled they plan to increase incursions into key Iraqi cities this fall - partly as a way for the United States to try to pressure insurgents into negotiations with Iraqi officials. U.S. Defense Secretary Donald Rumsfeld alluded to this last week when he said insurgencies in Fallujah and the city of Ramadi can be solved either diplomatically through negotiations, or through force.