BAGHDAD, Iraq - An explosion destroyed a car near an entrance to the headquarters of the U.S.-led coalition today, killing four people, the military said. An Iraqi policeman said they were foreigners.

About an hour later, at least two blasts were heard elsewhere in central Baghdad, and smoke rose from the vicinity of the Green Zone, which houses the coalition headquarters. A coalition spokeswoman said by telephone that she heard the blasts, but had no information on the cause.

In the car explosion, American soldiers tried to pull the men from the shattered vehicle and quickly sealed off the area, said witness Kamel Raji. The blast occurred about 50 yards from one of the main entrances to the Green Zone.

U.S. Army Col. John Murray said the explosion occurred about 2 p.m. and that the military was trying to identify the nationalities of the victims. He confirmed four deaths.

"We don't think it was a suicide bomber. We are still talking to eyewitnesses," Murray said.

Mohammed Naem, a noncommissioned police officer who saw the car explode, said the vehicle was a bulletproof Toyota Land Cruiser that was on its way to the convention center in the Green Zone.

Taxi driver Mohammed Saleh said he was about 20 yards away and heard shooting after the explosion.

"I saw the roof of the car flying," he said.

The bomb attack was the latest in a series of deadly assaults in the Iraqi capital.

On Saturday, a suicide car bomber in Baghdad killed four people and slightly wounded a deputy interior minister in Baghdad. On May 17, the president of the Iraqi Governing Council, Izzadine Saleem, was killed along with at least six other people near the coalition headquarters.

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

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

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

Some of the overnight combat occurred in the Revolution of 1920 Square and was so intense the steel fence between the square and an adjacent cemetery was destroyed. Three mortar rounds landed about 300 yards from the Imam Ali shrine, one of 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 in the first American incursion into Kufa.

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 killing of a moderate rival cleric in 2003, 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.

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 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.

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.