Iraqi police and Shi'ite militiamen have clashed in the southern holy city of Najaf, where a truce was reached two weeks ago to end a prolonged standoff with U.S. forces.

Local hospital officials say at least four people were killed, including one policeman, in the overnight fighting. More than a dozen people were wounded.

It was not clear what provoked the fighting.

U.S. troops were not involved in the clashes, following their agreement to end offensive operations in the city, pull back from holy sites and allow Iraqi police to secure the city.

Meanwhile, Iraqi Prime Minister Iyad Allawi condemned terrorist attacks over the last seven months on oil pipelines, which he said have cost the country more than $200 million.