Shiite leader Muqtada al-Sadr has hinted at retaliation if Iraqi Prime Minister Nouri al-Maliki's government does not immediately stop arresting his followers.
The anti-American cleric says in a statement issued Thursday in Najaf that the government has placed his movement in an impossible situation by demanding that followers stop military and political opposition and ignore the arrests and killings of supporters.
He says he is keen to prevent bloodshed but pointedly offers a reminder that his followers rose in the past against the "oppressors," referring to U.S. forces and last week's clashes against government forces in Basra.
Al-Sadr also called Thursday for a "million-strong" turnout for an anti-American demonstration April 9 to mark five years since the U.S.-led occupation in Iraq began.
The statement said protesters should head to the Shiite holy city of Najaf south of Baghdad waving Iraqi flags "to cement the unity of Iraq and demand its independence." It called on demonstrators to "raise your voices high in the skies of Iraq against the oppressing occupier," a term the Sadrists use to describe U.S.-led forces.
Al-Sadr also offered to help the government rid the army and police of what he says are terrorists and rival militiamen.
Al-Sadr complained in the statement that although he had called on his militia to stop fighting, the army and police were continuing illegal arrests and attacks against his followers.
Al-Sadr blamed the attacks on "corrupt elements" and said if the government could not remove them, "we are ready to cooperate...to purge our army and police of such elements."
Although major fighting in the south eased last weekend, military operations are continuing in the Basra area.
U.S. and Iraqi officials have maintained that the crackdown was directed at criminals and renegade militiamen but not al-Sadr's political movement, which holds 30 of the 275 seats in the national parliament and is a major political force.
But the Sadrists believed the operation was aimed at weakening their movement before provincial elections this fall. Resistance was so fierce that the Iraqis had to call in U.S. jets and British tanks and artillery to help in the battle.
On Thursday, the U.S. military said an American F/A-18 fighter jet fired a missile at a house in Basra the night before after Iraqi soldiers came under small-arms fire. Two militants were killed in the airstrike, the U.S. said.
"Coalition forces are unaware of any civilians killed in the strike but are currently looking into the matter," the military said. Iraqi witnesses and officials said at least three civilians were among the dead.
"While we were preparing for evening prayer, U.S. aircraft bombed this house, we rushed to save survivors but in vain," a neighbor identified only as Haj Juwad told AP Television News. "The father, mother and a young boy were killed and three others were buried under rubble. We evacuated two people and one is still under the rubble."
Hospital officials, who have strong ties to the Sadrists, said three bodies had been received, including two men and an elderly woman, and two women were wounded in the strike. The officials spoke on condition of anonymity because they weren't authorized to release the information.
In northern Iraq, officials said a suicide car bomber attacked an Iraqi checkpoint west of the city late Wednesday, killing seven people, including a woman and a 5-year-old child, and wounding 12, according to the Iraqi army.
The U.S. military confirmed the Mosul attack but put the casualty toll at five dead and 19 wounded.
In Baghdad, one civilian was killed and 10 were wounded in a parked car bombing, while an Iraqi soldier was killed and three were wounded when a roadside bomb struck their patrol.
Three Iraqi civilians also were wounded in a U.S. airstrike targeting militants engaged in a gunbattle with U.S. ground forces near the southern Shiite city of Hillah, according to a military statement.