Iraqi police arrested dozens of members of Shi'ite cleric Moqtada al-Sadr's Mehdi Army militia yesterday, hours after two policemen were killed in gunbattles in the southern city of Kut, police said.

Clashes this week between Iraqi security forces and the militia in Kut, 170 km southeast of Baghdad, have raised fears a ceasefire called by Sadr may unravel, although the violence has so far been confined to Kut.

It is the first major violation of the seven-month-old truce, which has been credited by the US military with helping to reduce violence between majority Shi'ite and Sunni Muslims that has killed tens of thousands of Iraqis.

Sadr clarified the conditions of the truce last week, telling followers they could defend themselves if attacked, an apparent response to complaints among his fighters that US and Iraqi forces were exploiting the ceasefire to target them.

"This operation started in the early morning and so far we have arrested 25 wanted people from the Mehdi Army," said Lieutenant Aziz al-Amara, who commands a rapid reaction unit.

Another police official, who declined to be named, said 70 people had been detained. There was a heavy presence of Iraqi and US forces in the city. US military spokesmen have given few details about their involvement in the clashes.

Police say at least 13 people have been killed in fighting since Tuesday.

Separately, the US military said eight Iraqi civilians were wounded in a rocket attack on a US facility in Hilla, 100 km south of Baghdad, late on Friday which Iraqi police blamed on an unspecified Shi'ite militia.