U.S. forces in Iraq are tightening their grip on the Shi'ite holy city of Najaf Friday, after a day of intensified fighting with armed followers of a wanted radical Shi'ite Muslim cleric, Moqtada al-Sadr.

American military officials say at least 41 militiamen were killed Thursday in battles on the outskirts of Najaf and the nearby town of Kufa. There also was fighting in Karbala -- another Shi'ite holy city to the north -- and in a Shi'ite neighborhood of Baghdad, the Iraqi capital.

U.S. forces captured the governor's office on the outskirts of Najaf, and the American civilian administrator for Iraq, Paul Bremer, quickly appointed a new governor, Adnan al-Zurufi, for the Najaf region -- a move apparently aimed at regaining control of the region from militia loyal to Mr. al-Sadr.

However, U.S. forces' operations in Najaf and Karbala have so far avoided the centers of those cities, where the holiest Shi'ite shrines are located.

Operations in Najaf began Thursday, just hours after Iraq's moderate Shi'ite leaders issued a statement calling on the radical cleric to withdraw his militias from the holy cities.

In another development, two foreign journalists -- one Polish and an Algerian -- were killed in a drive-by shooting and a bomb blast on a road south of Baghdad. Another Pole was wounded in the attack. A military spokesman for the Polish-led coalition force in southern Iraq said the three men worked for a Polish television station.