Thousands of angry mourners called for vengeance as they gathered outside Iraq's holiest Shiite shrine where yesterday a car bomb killed more than 100 people, including one of country's most senior Shia Muslim clerics.

The bomb also injured more than 140, at the Imam Ali mosque in Najaf as Ayatollah Mohammed Baqir al-Hakim emerged after delivering a sermon calling for Iraqi unity.

"Our leader al-Hakim is gone. We want the blood of al-Hakim," a crowd of 4,000 men beating their chests chanted in unison outside the mosque today.

Tens of thousands of worshippers filled the shrine and the surrounding streets for a funeral service for Ayatollah Hakim and other blast victims later Saturday. The main road leading to the shrine was open only to pedestrians, and residents carried coffins on the tops of cars and backs of trucks for the funeral service.

Iraqi police arrested four men in connection with the bombing, all on whom have connections to Osama bin Laden's al-Qa'ida network, a senior police official told The Associated Press.

The official, who said the death toll in the bombing had risen to 107, said the four arrested men — two Iraqis and two Saudis — were caught shortly after the explosion.

The police official, who led the initial investigation and interrogation of the captives, said the prisoners told of plans to kill political and religious leaders and to damage vital installations such as electricity generation plants, water supplies and oil pipelines.

The official, who refused to be named, said the bomb was made from the same type of materials used in the bombing at the UN headquarters in Baghdad, in which at least 23 people died, and the Jordanian Embassy attack in which 19 people died.

People were last night digging among the rubble for survivors, but all they found were severed human limbs and body parts. The attack killed more people than the bombings at the United Nations and the Jordanian embassy put together.

The bomb was set off outside the holy shrine, the resting place of one of Shia Islam's two most revered saints. The blast was so powerful it damaged shops across the street, blew a deep crater in the ground and smashed several cars to pieces. Decorative work outside the shrine was also damaged.

There will be fears the death of Ayatollah Hakim could set off violence in Najaf, a city riven by competing factions trying to set themselves up as the Shia leadership. Some blamed the bombing on Sunni Muslim supporters of Saddam Hussein, the former Iraqi president. Ayatollah Hakim was the leader of the Iranian-backed Supreme Council for the Islamic Revolution in Iraq (SCIRI), one of the more powerful Shia factions.

His brother, Abdel Aziz al-Hakim, is a member of Iraq's American-appointed "Governing Council".