Baghdad, Iraq ? The U.S. military said Saturday it killed 18 gunmen believed loyal to radical cleric Muqtada al-Sadr in Baghdad, and jet fighters bombarded militia positions on the capital’s outskirts. Skirmishes persisted in the southern holy cities of Najaf and Karbala.

The U.S. military also announced the deaths of five soldiers, including three killed by rebel attacks. In northern Iraq, rebels fired a mortar round at an Iraqi army recruiting center, killing four volunteers, hospital officials said.

U.S. troops are trying to disband the cleric’s army and sideline its radical leadership before handing power to a new Iraqi government June 30. Al-Sadr is a fierce opponent of the U.S.-led occupation who launched an uprising last month and faces an arrest warrant in the death of a rival moderate cleric last year.

In Najaf, militiamen fired a rocket-propelled grenade at a U.S. tank stationed at the city’s Police Directorate. The rocket missed its target, and the two sides exchanged gunfire. Elsewhere, a shell landed on a house, wounding a woman.

The normally bustling area around Karbala’s Imam Hussein shrine, one of the holiest centers for Shiite Muslims, was silent except for intermittent blasts and machine-gun fire. After one blast, a huge column of black smoke wafted over the golden-domed shrine. One Polish soldier was wounded in Saturday’s skirmishes, the Polish military said in Warsaw.

The confrontations in the two holy cities in Iraq’s southern Shiite heartland were less intense than in previous days.