BAGHDAD - U.S. and Iraqi forces swooped into a mosque complex in eastern Baghdad yesterday and detained a top aide to radical anti-American cleric Muqtada al-Sadr, the latest in a series of operations aimed at eviscerating the leadership of the Mahdi Army militia.

The raid drew immediate criticism from the Iraqi government, which complained that it had not been consulted. An aide to Prime Minister Nouri al-Maliki, who owes his job as Iraqi leader to Sadr's backing, said the operation was not part of a coming U.S.-Iraq security drive.

Under the plan, to which President Bush has committed 21,500 troops, U.S. commanders have been promised a freer hand against both Sunni insurgents and Shiite militiamen.

"There was no coordination with the Iraqi political leadership, and this arrest was not part of the new security plan," Sadiq al-Rikabi, the Maliki adviser, told Al-Arabiya television. "Coordination with the Iraqi political leadership is needed before conducting such operations that draw popular reactions."

Abdul-Hadi al-Darraji was captured in the early-morning raid, and his bodyguard was killed in what Abdul-Zahra al-Suweiadi, a senior Sadr aide, called a "cowardly act." Sadr's office said Darraji was media director for the cleric's political movement and demanded his immediate release.

"America is playing with fire, and our patience is beginning to fade," said Abdul-Razzaq al-Nidawi, a Sadr aide in the Shiite holy city of Najaf. "This savage barbarian act will not pass peacefully."

The U.S. military, in a statement that did not name Darraji or mention the Mahdi Army by name, said special Iraqi army forces operating with U.S. advisers had "captured a high-level, illegal armed group leader" in Baghdad's Baladiyat neighborhood, which is adjacent to Sadr City, the Mahdi Army stronghold.

"Iraqi forces detained him based on credible intelligence that he is the leader of an illegal armed group [involved in] . . . the organized kidnapping, torture and murder of Iraqi civilians," the U.S. statement said. "The suspect is also reportedly involved in the assassination of numerous Iraqi Security Forces members and government officials."

It said two other suspects were detained.

In an interview with an Italian newspaper, Sadr said the U.S.-Iraqi security crackdown already had begun. And he confirmed reports that 400 Mahdi Army fighters had been arrested.

The La Repubblica interviewer quoted Sadr as saying he feared for his life and stayed on the move constantly. Sadr said his militias would not fight back immediately because Islam forbids killing during the Muslim holy month of Muharram, which started yesterday for Sunnis and today for Shiites.

"Let them kill us," he was quoted as saying. "For a true believer there is no better moment than this to die: Heaven is ensured. After Muharram, we'll see."

At least 27 people were killed or found dead as a result of sectarian violence across Iraq yesterday. Gunmen attacked a Shiite mosque in southern Baghdad, killing two guards and setting off explosives to damage the building.

A roadside bomb killed one U.S. soldier and wounded three in an attack Thursday against a patrol that was escorting a convoy in northwestern Baghdad, the military said yesterday.