Hours before the raid in Baghdad near Sadr City, al-Sadr personally was the apparent target of a mortar attack at his home in the holy city of Najaf, 90 miles south of Baghdad.

At least one mortar round struck within yards of al-Sadr's home, wounding a guard and a passing child, said Sheik Sahib al-Amiri, an aide to the cleric.

Shortly after the attack, al-Sadr issued a statement calling for calm.

"I call upon all brothers to stay calm and I call upon the Iraqi army to protect the pilgrims as the Nawasib (militants) are aiming to attack Shiites every day," he said, referring to Wednesday's commemoration marking the death of the Prophet Muhammad.

Following the raid, Prime Minister Ibrahim al-Jaafari, a Shiite, expressed concern and telephoned Iraqi military leaders and US Gen. George Casey to "discuss the situation," said spokesman Abdul Rezzaq Al-Kadhimi.

He said the prime minister promised government compensation for families of those killed in the raid and called for Iraqis to be patient until an investigation was completed.

Police Lt. Hassan Hmoud, who put the death toll at 22, said some of the casualties were at the Islamic Dawa Party-Iraq Organization office near the mosque. The incident started when US forces came under fire from the direction of the mosque and the party office, he said. The party is a separate organization from the one headed by al-Jaafari.

Shiite legislator and party spokesman, Khudayer al-Khuzai, said 15 members of the party were holding a "cultural meeting" in an office near the Shiite mosque. "They have nothing to do with the acts of violence," he said.

Al-Khuzai claimed that after coming under attack, US forces raided the party office, "tortured" the men, dragged them out and "executed" them. He said it was not clear who attacked the US troops.

The main Shiite political bloc, the United Iraqi Alliance, would demand a quick investigation "because the Iraqi blood is not cheap," al-Khuzai said.

Lt. Col. Barry Johnson, a US military spokesman, denied that the troops targeted a party office.

"The building was not a party headquarters but a community meeting room, and there was substantial intelligence on this building showing that that was not, in fact, what it was used for," he said.

In the north of the country, meanwhile, the Kurdish writer Kamal Karim was handed an 18-month sentence for articles on a Kurdish Web site that accused Masoud Barazani, one of the region's top leaders, of corruption.