Shiite leader Muqtada al-Sadr wants a "political solution" to the crisis that has led to deadly clashes between his followers and government security forces this week in Baghdad and the oil-rich south.
In a brief statement released in this holy Shiite city south of Baghdad, al-Sadr said he wants "everyone to pursue political solutions and peaceful protests and a stop to the shedding of Iraqi blood."
The statement was relayed to he media by al-Sadr's close aide Hazem al-Aaraji.
Earlier Thursday, Iraq's prime minister vowed to fight "until the end" against Shiite militias in Basra despite protests by tens of thousands of followers of a radical cleric in Baghdad and deadly clashes across the capital and the oil-rich south.
Mounting anger focused on Prime Minister Nouri al-Maliki, who is personally overseeing operations against the militias dominated by al-Sadr's supporters amid a violent power struggle in Basra, Iraq's southern oil hub.
The Iraqi leader made his pledge to tribal leaders in the Basra area as military operations continued for a fourth day with stiff resistance.
"We have made up our minds to enter this battle and we will continue until the end. No retreat," he said in a speech broadcast on Iraqi state TV.
The events threatened to unravel a Mahdi Army cease-fire and lead to a dramatic escalation in violence after a period of relative calm that had lasted for months.
Sadrist lawmakers in Baghdad issued a strongly worded statement demanding a halt to the military operations and appealing to Iraqi security forces to stand down.
"We call on our brothers in the Iraqi army and the brave national police not to be tools of death in the hands of the new dictatorship," Sadrist lawmaker Falah Shanshal said.
The crisis was seen as a test of the Iraqi government's ability to eventually take over its own security. The U.S.-led coalition has a minimal presence in Basra after British forces turned over responsibility for the area to the Iraqis in late December.
Demonstrators in the northern Baghdad neighborhood of Kazimiyah called al-Maliki a "new dictator" as they carried a coffin bearing a crossed-out picture of the U.S.-backed prime minister, who belongs to a rival political party. A sea of people also rallied in Sadr City, Baghdad's main Shiite district.
Suspected Shiite extremists also continued to hammer the U.S.-protected Green Zone, firing several rounds of apparent rockets that sent a huge plume of smoke above the heavily fortified area in central Baghdad.
No casualties were immediately reported Thursday, but the military said a U.S. soldier, two American civilians and an Iraqi soldier were wounded in a volley the day before. An American financial analyst was killed Sunday in attacks on the Green Zone.
Meanwhile, gunmen kidnapped an Iraqi civilian spokesman for Baghdad security operations Thursday and killed three of his bodyguards after torching his house in a Mahdi Army stronghold in the capital.
The attack targeted Tahseen Sheikhly, a Sunni who often appeared with U.S. military and embassy officials at news conferences to tout the successes of the crackdown on sectarian violence that began in February 2007.
The demonstrating Sadrists are angry over recent raids and detentions, saying U.S. and Iraqi forces have taken advantage of the August cease-fire to crack down on the movement.
They have accused rival Shiite parties, which control Iraqi security forces, of engineering the arrests to prevent them from mounting an effective campaign after the Iraqi parliament agreed in February to hold provincial elections by the fall.
U.S. commanders have insisted the fight is being led by the Iraqi government and was not against al-Sadr's movement but breakaway factions believed to be funded and trained by Iran, which has denied the allegations.
Al-Maliki has warned gunmen in Basra to surrender their weapons by Friday or face harsher measures.
Despite the ultimatum, heavy gunfire and explosions resounded across Basra while helicopters and jet fighters buzzed overhead. The city's police chief escaped an assassination attempt late Thursday but three of his guards were killed in the roadside bombing.
Government troops have faced stiff resistance in neighborhoods controlled by the Mahdi Army in Basra, Iraq's second-largest city, 340 miles southeast of Baghdad. Residents spoke of militiamen using mortar shells, sniper fire, roadside bombs and rocket-propelled grenades to fight off security forces.
A Pentagon official said Wednesday that reports from the Basra area indicate that militiamen had overrun a number of police stations. The official spoke on condition of anonymity because he was not authorized to discuss the matter publicly.
Street battles that started Tuesday in Basra and Sadr City have spread to several other neighborhoods and southern cities, leaving more than 200 dead, including civilians, Iraqi troops and militants. That three-day figure was a rough estimate provided by police and hospital officials who could not give a more specific breakdown.
Iraqi officials reported 17 more people killed in overnight clashes in Sadr City, raising the total there to 40.
The death toll in the Shiite city of Hillah, 60 miles south of Baghdad, also rose to at least 60 in fighting that continued into Thursday, according to a senior police official who asked not to be identified because of security concerns.
The U.S. military said four suspected Shiite extremists were killed in an airstrike but it had no further details.
The police chief in Kut, Abdul-Hanin al-Amara said 40 gunmen had been killed and 75 others wounded in that southeastern city.
A bomb struck an oil pipeline Thursday in Basra, a local oil official said, declining to be identified because he was not authorized to release the information.
Iraqi Oil Minister Hussein al-Shahristani, however, sought to assure international oil companies. The security situation in Basra "is still unstable ... but this has not reflected negatively (on) works at oil output and export installations," al-Shahristani told the U.S.-funded Radio Sawa.
In other violence reported by police, a booby-trapped car exploded near the Iraqi Red Crescent Society's offices in Baghdad, killing two civilians and wounding five.
Gunmen also killed a U.S.-allied Sunni fighter and wounded his wife and daughter after storming his house in the northern city of Samarra late Wednesday.