A roadside bomb blast and a brief gunfight in the Iraqi town Fallujah have left at least two civilians dead and four people wounded, including two U.S. soldiers.

The U.S. military said fighting broke out when coalition troops were ambushed as they entered the town shortly after midnight. Insurgents detonated a roadside bomb and opened small arms fire, wounding two soldiers and destroying a vehicle.

Residents said a number of houses were damaged and sounds of gunfire and explosions echoed around the town for several hours after the attack.

Fallujah, located about 50 kilomters west of Baghdad, has been the site of frequent anti-coalition violence since U.S.-led forces ousted the regime of Saddam Hussein nearly a year ago.

Hours later, in northern Iraq, two bombs exploded in the town of Mosul. Iraqi police said at least three policemen were wounded in one of the roadside blasts. They said the second explosion damaged a U.S. military vehicle and wounded its Iraqi driver.

And, in Baghdad, a hotel housing foreign contractors and journalists was hit by a rocket. The blast caused little damage and no casualties. Foreign contractors and journalists frequently stay in the hotel.

Sirens also sounded briefly in the Green Zone, which houses the headquarters of the U.S.-led coalition. In recent weeks, there has been a sharp rise in attacks against Iraqi security personnel and others working with the U.S. -led Iraqi occupation authority.

On Tuesday, 11 people were killed in two separate insurgent attacks -- in Mussayab, south of Baghdad, and in the northern city of Kirkuk. Among the victims, nine were police trainees and the other two, policemen.