American AC-130 gunships and tanks battled militiamen near shrines in the Shiite holy city Karbala, and fighting was heavy in two other towns south of Baghdad.
In Karbala, the U.S. military said it killed 18 fighters loyal to cleric Muqtada al-Sadr, who launched an uprising against the American-led coalition in early April and is wanted in the murder of a rival moderate cleric last year. Hospital officials reported 12 deaths, including two Iranian pilgrims. A driver for the Arab television network Al-Jazeera was also killed.
Much of the fighting in Karbala was near the city's Imam Hussein and Imam Abbas shrines, which U.S. forces say are being used by militiamen as firing positions or protective cover.
At least six people were killed and 56 were injured in fighting in Najaf and neighboring Kufa, where al-Sadr delivered a defiant sermon to 15,000 worshippers in which he urged his supporters to resist the coalition.
In other developments:
The fighting in Karbala started after insurgents fired several rocket-propelled grenades at U.S. tanks that were patrolling on the outskirts of the so-called "Old City," a maze of alleyways and cluttered buildings, said U.S. Army Col. Pete Mansoor of the 1st Armored Division.
The tanks returned fire, and more than two hours of heavy fighting followed. Smoke billowed from burning buildings. Explosions lit up the night sky and reverberated throughout the city. Electric lights flickered on and off. By 3 a.m., the fighting had stopped.
Much of the fighting was near the city's Imam Hussein and Imam Abbas shrines, which U.S. forces allege are being used by militiamen as firing positions or protective cover. Mansoor said the shrines were not damaged.
The military says it is doing its best to avoid damage to the gold-domed shrines, which could infuriate Shiite Muslims who are not involved in the conflict. Al-Sadr, who launched an uprising against the U.S.-led occupation of Iraq last month, has accused U.S. forces of desecrating holy sites.
"Don't let my killing or arrest be an excuse to end what you're doing, supporting the truth and standing up to the wrong," al-Sadr said in a sermon to 15,000 worshippers at Friday prayers in the city of Kufa.
Two people died in fighting in Kufa, witnesses said.
One civilian died and another was injured in Najaf when their car was caught in fighting, hospital officials said. At least 14 people were injured.
Mansoor said 18 insurgents died in Karbala. Dr. Abbas Falih al-Hassani of Karbala's al-Hussein hospital said 12 people died, including two Iranian pilgrims. Thirteen were injured.
The dead included a driver for a camera crew of the Al-Jazeera television network, the station reported.
Rashid Hamid Wali died while assisting a crew from the Qatar-based network that was filming the clashes from a hotel roof shortly after midnight, said Ahmed al-Sheikh, the network's news editor in Qatar.
In a statement, Al-Jazeera said 38-year-old Wali died after a bullet penetrated his left eye and came out of the back of his head. It said Wali was shot while peering down from the hotel roof as American armored vehicles moved in the street.
Saad Ibrahim, a producer in Al-Jazeera's Baghdad office, said Wali was killed by fire from an American tank. The military had no comment.
U.S. troops pulled out of the Mukhayam mosque in Karbala, the scene of fierce fighting last week during which coalition forces ousted insurgents who were using it as a base of operations. Since then, American soldiers there have come under frequent attack.
The military said it planned to conduct regular patrols in Karbala despite the withdrawal.
The mosque pullout happened hours after a major military operation into Karbala was postponed. The operation was postponed to allow discussion between Iraqi leaders and al-Sadr's militia on a possible negotiated end to the fighting, a senior military official said on condition of anonymity.
Officers said soldiers operating in Karbala's Old City in the past two weeks experienced intense urban combat similar to battles in Mogadishu, Somalia, more than a decade ago.
The U.S. military says al-Sadr, who is wanted in the murder of a rival moderate cleric last year, must disband his militia. Al-Sadr has refused.