BAGHDAD Shi'ite cleric Moqtada al-Sadr suspended all armed actions by his Mehdi Army on Wednesday to remove rogue elements from the militia after 52 people were killed in gun battles in the southern Iraqi city of Kerbala.
Asked if the unexpected order meant no attacks on U.S. troops, one senior aide who declined to be identified said: "All kinds of armed actions are to be frozen, without exception."
The battles on Tuesday appeared to pit Iraq's two biggest Shi'ite groups against each other -- followers of Sadr and his Mehdi Army, and the rival Supreme Iraqi Islamic Council (SIIC), whose armed wing controls police in much of the south.
"The aim is to remove bad members who are involved in the Mehdi Army and working for their personal interests ... to hurt the Mehdi Army's reputation," said another aide.
Analysts said the test of the six-month suspension order would be whether his fighters obeyed because it was no longer clear how much authority Sadr exercised over the Mehdi Army.
It is believed to have fragmented and the U.S. military says rogue factions receive funding, training and weapons from Iran.
Shi'ite Prime Minister Nuri al-Maliki said on Wednesday militants involved in the violence in Kerbala wanted to blow up the Imam Hussein shrine, one of the holiest to Shi'ite Muslims.
"From our initial investigation, we found some evidence of who did this act... the intention of this act was to storm into the shrine of Imam Hussein and blow it up," Maliki said from inside the shrine during a visit to Kerbala, 110 km (68 miles) south of Baghdad.
Iraqi national security adviser welcomed Sadr's suspension order but said it would need to be carried out.
"If it happens it will reduce the violence in the country by a great deal," Mowaffaq al-Rubaie told CNN.
The Pentagon earlier this year called the Mehdi Army, which has thousands of gunmen, the greatest threat to peace in Iraq.
A third Sadr aide, Hazim al-Araji, said Sadr had ordered all his movement's offices to close for three days of mourning following the fighting around two shrines.
Sadr, a youthful, fiery anti-American cleric, set up the Mehdi Army in 2003 after the U.S.-led invasion of Iraq.
A year later, he led his militia in two uprisings against U.S. forces before getting involved in mainstream politics. He played a key role in Maliki's rise to power in 2006.
In a split with Maliki, Sadr withdrew his six ministers from the cabinet in April when the prime minister refused to set a timetable for the withdrawal of U.S. troops from Iraq.
Joost Hiltermann, a Middle East analyst with the International Crisis Group think tank, said Sadr wanted to distance himself from what happened in Kerbala.
"What happened yesterday went a bit too far because it involved the holy shrines," Hiltermann said, referring to the violence around the Imam Hussein and Imam Abbas shrines, two of the holiest in Shi'ite Islam.
"He's showing that he's not in control of these forces. He's embarrassed by it, it's a loose element and he wants to restore control. The question is really whether they will listen."
Earlier, Maliki announced his forces had restored order in the city. The violence among Shi'ites had spread overnight, with gunmen attacking SIIC offices in at least five cities.
Maliki blamed "outlawed armed criminal gangs from the remnants of the buried Saddam regime" for the violence and sacked the army general in charge of the Kerbala command centre.
The rogue groups in the militia, while proclaiming loyalty to Sadr, have their own violent agenda. Some are seen as little more than criminal gangs.
Mehdi Army fighters have avoided confrontation with U.S. forces and kept a relatively low profile since the start of a large-scale security crackdown in February.
While his ministers have left the cabinet, the cleric's political bloc holds 30 seats in parliament and is still part of the ruling Shi'ite Alliance.
(Additional reporting by Ahmed Rasheed, Peter Graff and Ross Colvin)