US and Iraqi forces arrested one of Muqtada al-Sadr's top aides Friday in Baghdad, his office said, as pressure increases on the radical Shiite cleric's militia ahead of a planned security sweep aimed at stemming the sectarian violence ransacking the capital. Sheik Abdul-Hadi al-Darraji, al-Sadr's media director in Baghdad, was captured Friday and his personal guard was killed, according to another senior al-Sadr aide. "We strongly condemn this cowardly act," Sheik Abdul-Zahra al-Suweiadi said. 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 came 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. Two Shiite militia commanders said Thursday that al-Maliki has stopped protecting the militia under pressure from Washington, while the fighters described themselves as under siege in their Sadr City stronghold. 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 Diraa, a Shiite militia leader who has gained a reputation for his brutality. Al-Suweiadi did not give more details, but another official in al-Sadr's office said al-Darraji was captured during a 2 a.m. raid on a mosque in the eastern neighborhood of Baladiyat, less than a kilometer (a mile from a US base.) The official and an Iraqi police officer, who spoke on condition of anonymity because of security concerns, 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. Abdul-Razzaq al-Nidawi, an al-Sadr aide in the Shiite holy city of Najaf, demanded that al-Darraji and other detainees from the cleric's movement, be released and called for demonstrations after the weekly Friday prayer services. "America is playing with fire and our patience is beginning to fade," he said. "This savage barbarian act will not pass peacefully."