At least nine Iraqis were killed and 16 others injured in fierce clashes between US forces and gunmen overnight in Falluja, west of Baghdad, according to hospital officials.
Dr Ahmed Abdullah, a doctor at Falluja general hospital, said some of the wounded were in a serious condition after the fighting, which residents said lasted several hours and destroyed houses and factory buildings in the east of the city.
Another hospital doctor said 10 people had died in the fighting, which largely took place in an industrial area.
Calls of "God is great" echoed from mosques as US aircraft and tanks attacked, residents said.
A US military spokesman said that Iraqi security forces and US marines had clashed with insurgents and an air strike had been called in on a target in eastern Falluja.
He said fighters had attacked a US position with mortars, rocket-propelled grenades, machine guns and small arms. US forces responded with tank and artillery fire.
After fierce clashes in Falluja in April that killed hundreds of Iraqis, US forces withdrew from the city and handed over security to an Iraqi force.
Critics say the city has since become a safe haven for guerrillas and kidnappers. In recent months US forces have attacked buildings in the city they say were being used by militants linked to al-Qaeda ally Abu Musab al-Zarqawi.