Iraqi rebel cleric Moqtada al-Sadr called for a truce to be restored after a day of clashes between his followers and coalition forces in Baghdad, Basra and the holy city of Najaf.
US forces have moved into Baghdad's Sadr City and British forces have surrounded the office of the militant cleric Muqtada al-Sadr in Basra.
At least 17 people have been killed and more than 100 others were injured in the clashes.
Earlier an American helicopter was shot down in heavy fighting in the central Iraqi city of Najaf. The helicopter was shot down by followers of the rebel cleric, Moqtada al-Sadr.
Meanwhile, a doctor was killed and four other people were seriously wounded when rockets were fired at the general hospital in Najaf. It is not clear who was responsible.
It was the heaviest fighting in Najaf since May. The city is home to the holiest shrines in Shi'ite Islam.
