U.S. and Iraqi forces have begun an operation in the city of Diwaniya, south of Baghdad, to bring the volatile Shi'ite town under government control.
The U.S. military says Iraqi army troops backed by U.S. forces moved into the city early Friday morning to disrupt activities of a Shi'ite militia loyal to anti-American cleric Moqtada al-Sadr.
City residents reported of fighting between militia gunmen and coalition troops. They said soldiers also were conducting house-to-house searches and making arrests, after imposing a strict curfew.
There were no immediate report of casualties.
Separately, a suicide car bomber struck a police checkpoint in western Ramadi Friday, killing at least 20 people and wounding 30 others.
A top local police official said two policemen were among the dead.
Ramadi is the capital of the restive Al Anbar province, which has been a stronghold of Sunni insurgency. But recently many tribes have switched sides and joined the Iraqi police and army in an attempt to expel al-Qaida in Iraq fighters from their region.
Some information for this report was provided by AP and Reuters.