Clashes between U.S. forces and fighters loyal to rebel cleric Muqtada al-Sadr (search) overnight in the holy city of Najaf left at least one person dead and 20 injured, a hospital official said Monday.

The official, Fadhil Abbas, said the toll was likely to rise because ambulances had been dispatched to recover more casualties. He also said that the hospital was waiting for relatives of four people killed in clashes on the previous night to come to identify the bodies, which had been decapitated.

Also Monday, an explosion was heard in central Baghdad. Smoke rose from a burning car near an entrance to the U.S.-led coalition headquarters, witnesses said. It was unclear if there were casualties.

An Associated Press photographer said the burning car was near a main entrance to the coalition compound, about 100 yards from the Baghdad Convention Center.

There were no reports of U.S. casualties in the fighting in Najaf (search), south of Baghdad.

Some of the overnight combat occurred in the Revolution of 1920 Square and was so intense that the steel fence between the square and the adjacent cemetery was destroyed. Three mortar rounds landed about 300 yards from the Imam Ali shrine, one of Shia Islam's holiest sites. Witnesses said there were no casualties.

On Sunday, U.S. and Iraqi security forces raided a mosque in neighboring Kufa, where they said insurgents stored weapons. The military said at least 32 al-Sadr fighters were killed during the first American incursion into Kufa (search).

In another holy city, Karbala, militia fighters appeared to have abandoned their positions after weeks of combat.

Al-Sadr launched an uprising against the coalition early last month. Sought for the April 2003 killing of a moderate rival cleric, al-Sadr has taken refuge in Najaf and routinely delivers a Friday sermon in Kufa.

A U.S. Marine was killed and several other troops were injured when a bomb hidden in a parked car exploded as two American convoys passed Sunday near Fallujah, west of Baghdad. After heavy fighting last month, Marines withdrew from Fallujah and announced that an Iraqi force led by former officers in Saddam Hussein's army would patrol the Sunni-dominated city.

U.S. troops also battled militiamen in a Shiite district of Baghdad on Sunday. Nine U.S. soldiers were wounded around the city, the military said, including four injured in a mortar attack in the east of the capital.

In the Sunday raid in Kufa, U.S. soldiers fought militiamen near the Sahla mosque and then raided it for weapons after an Iraqi counterterrorism force "cleared" the site, the military said. Soldiers seized a machine gun, two mortar tubes and more than 200 mortar rounds, along with rocket-propelled grenade launchers and rounds, according to a statement.

American troops smashed the gate to the mosque complex with an armored vehicle and killed people inside, mosque employee Radhi Mohammed said. An Associated Press photographer saw bloodstains on the ground indicating that someone was dragged for at least 10 yards. There also was blood in mosque bathrooms.

The fighting around Shiite holy cities south of Baghdad, among the world's most sacred Shia sites, has enraged Shiite communities in Iran and elsewhere.

In Tehran, Iranian Foreign Ministry spokesman Hamid Reza Asefi said Iran sent a "warning" message to the United States through the Swiss Embassy concerning American actions in Iraq. Switzerland looks after American interests in Iran. Asefi did not say whether the warning involved military actions around the holy cities.

Maj. Gen. Martin Dempsey, commander of the 1st Armored Division, said U.S. forces took care not to damage Shiite Muslim shrines even though militiamen used them as fighting positions.

The U.S. military command denied a Washington Post report Sunday that the top American general in Iraq, Lt. Gen. Ricardo S. Sanchez, was present during some interrogations at the Abu Ghraib prison and witnessed some abuses of Iraqi inmates.

"This report is false," the U.S. military said in a statement.

Sanchez stands by his testimony before congressional committees that he was unaware of the abuses until ordering an investigation into the allegations in January, the military said.