At least four people were killed and 54 wounded on Monday in clashes between gunmen loyal to cleric Moqtada al Sadr and police in the southern Shi'ite city of Nassiriya, hospital sources and police said.
The sources said the clashes erupted overnight when police attacked a Sadr office in Nassiriya in an apparent response to an attack on the head of police which left him wounded.
The sources said the police accused the Mehdi Army of attacking the head of police.
Nassiriya is one of Iraq's oil rich cities and has been relatively calm. Last year, Italian troops handed over security in the city to Iraqi forces.