US and Iraqi forces have begun an offensive in Mosul to retake control of rebel-held areas after a week of anarchy in Iraq's third largest city.
"Offensive operations have begun on the western side of the river to clear out final pockets of insurgent fighting," said a spokeswoman for US forces in the north.
"It's a significant operation to secure police stations in the area and make sure they can be put to use again."
Violence in Mosul was part of a surge in unrest in Sunni areas of Iraq that coincided with a major US assault on the rebel bastion of Falluja. The US military says it has taken control of Fallujah, but scattered resistance remains.
This morning a marine was killed in a suicide car bomb attack in the south of Fallujah. At least 39 US troops have been killed since the start of the Fallujah offensive eight days ago.
US and Iraqi forces had met little rebel resistance in the early stages of the Mosul operation but said a curfew would remain in place and that the five bridges over the Tigris in the city were closed, the military said.
Last week scores of guerrillas seized control of parts of the city, attacking police stations, looting them of weapons and flak jackets and setting them ablaze. Nine of 33 police stations were overrun, and some were briefly held by insurgents.
A few hundred US troops, backed by Iraqi national guards and a unit of police special commandos were involved in today's operation, which would continue until all police stations were secure and insurgents defeated, the US spokeswoman said.
A US brigade, around 5,000 soldiers, and a brigade of Iraqi national guards had been assigned to the operation, but only a fraction of those assets were being used, she said.