U.S. and Iraqi forces launched an offensive in Mosul on Tuesday to retake control of rebel-held areas after a week of anarchy with insurgents rampaging through 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 Captain Angela Bowman, spokeswoman for U.S. 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." U.S. and Iraqi forces had met little rebel resistance in the early stages of the Mosul operation but said a 4 p.m. to 6 a.m. (1300-0300 GMT) curfew would remain in place and that the five bridges over the Tigris in the city were closed, Bowman 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 U.S. troops, backed by Iraqi national guards and a unit of police special commandos were involved in Tuesday's operation, which would continue until all police stations were secure and insurgents defeated, Bowman said. A U.S. 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.