BAGHDAD, Iraq - US and Iraqi forces arrested a top aide to radical Shiite cleric Muqtada al-Sadr on Friday in Baghdad, his office said.

The sign at the entrance to Camp Pendleton Marine Corps Base in California. A US Marine pleaded guilty to murder and other charges connected to the death of an Iraqi civilian outside Baghdad last year.[AFP]

Sheik Abdul-Hadi al-Darraji, al-Sadr's media director in Baghdad, was captured during a 2 a.m. raid on a mosque in the eastern neighborhood of Baladiyat, an official in al-Sadr's office said, speaking on condition of anonymity because of security concerns.

The US military said special Iraqi army forces operating with coalition advisers captured a high-level, illegal armed group leader in Baladiyat, but it did not identify the detainee. It said two other suspects were detained by Iraqi forces for further questioning.

The raid comes as Prime Minister Nouri al-Maliki has pledged to crack down on Shiite militias as well as Sunni insurgents in a planned security operation to quell the sectarian violence in Baghdad amid concerns that his reluctance to confront the Mahdi Army of his political backer al-Sadr led to the failure of two previous crackdowns.

The US military accused the main suspect of having ties with the commanders of so-called death squads, which have been blamed for many of the killings that have left dozens of bodies, often showing signs of torture, on the streets of Baghdad.

The suspect was detained "based on credible intelligence that he is the leader of illegal armed group punishment committee activity, involving the organized kidnapping, torture and murder of Iraqi civilians," according to the military statement.

It also said he was reportedly involved in the assassination of numerous Iraqi security forces and government officials.

"The suspect allegedly leads various illegal armed group operations and is affiliated with illegal armed group cells targeting Iraqi civilians for sectarian attacks and violence," the statement said, adding he was believed to be affiliated with Baghdad death squad commanders, including Abu Dura, a Shiite militia leader who has gained a reputation for his brutality.

The official and an Iraqi police officer, who also declined to be identified for fear of reprisals, also said one of the mosque's guards was killed in a firefight during the raid that damaged the mosque walls, while four other people who were with the sheik were arrested.