BAGHDAD ø The U.S. military says it has expelled an Iranian-backed Shi'ite force from major Iraqi cities.

U.S. officials said U.S. and coalition troops have forced the Mahdi Army, led by Iranian-backed cleric Moqtada Sadr, out of such Shi'ite cities as Karbala, Kut and Najaf. They said the Shi'ite force, which numbers up to 10,000, withdrew under U.S. fire over the last three days.

Over the last week, the U.S. military accelerated operations in an effort to dislodge the Mahdi Army from major Shi'ite cities. U.S. troops in Kufa and Najaf battled Mahdi Army units composed of up to five people armed with rocket-propelled grenade and automatic weapons. More than 150 Mahdi fighters were said to have been killed over the last week, Middle East Newsline reported.

In Karbala, the Mahdi Army appeared to have completely withdrawn from the central Iraqi city, officials said. But they did not rule out that Mahdi combatants had merely removed their uniforms and remained in the city with their weapons.

"Since then Iraqi police have begun patrolling the city, and it would appear that life ø normal life is returning to the city of Karbala, absent the militia that had been holding the city hostage for so many weeks," Brig. Gen. Mark Kimmitt, deputy director of coalition operations, said.

Kimmitt said the Mahdi Army has also been equipped with mortars and anti-aircraft guns. The U.S. brigadier said coalition forces destroyed two 120 mm mortars and a 57 mm anti-aircraft gun in Karbala on May 23.

The U.S. operation has included the use of what Kimmitt termed Iraqi counterterrorism forces to enter Shi'ite mosques, where the Mahdi Army had stored weapons. Kimmitt said Iraqi forces found a significant weapons cache in a mosque in Kufa and captured 10 Mahdi Army combatants, including a suspected commander.

The U.S. military campaign began after Shi'ite leaders called for the withdrawal of the Mahdi Army from their cities. The Shi'ites have organized marches against Sadr and in some cases were said to have provided intelligence information that facilitated the search for weapons stored by his militia.

Officials said Iraqi Civil Defense Corps members have also joined the operation to expel the Mahdi Army. They said ICDC units conducted checkpoints north and south of Al Dur in southeastern Iraq in an effort to prevent the escape of Sadr's forces.

This marked the first major deployment of Iraqi security forces since the Shi'ite revolt in April in which ICDC units collapsed and members defected to the Mahdi Army. Officials said the Iraqi forces have been used for missions in and around Shi'ite mosques to avoid friction with the local population.

"As challenges arise in Falujah, Najaf, and elsewhere, the tactics of our military will be flexible," President George Bush told the U.S. Army War College on Monday. "Commanders on the ground will pay close attention to local conditions. And we will do all that is necessary - by measured force or overwhelming force ø to achieve a stable Iraq."