An aide to radical Shiite Muslim cleric Muqtada al-Sadr (search) warned Friday that his supporters could rise up again if Iraqi authorities continue raiding his offices and detaining his followers.

Earlier this week, U.S. troops raided al-Sadr's office in the southern holy city of Najaf (search) and detained about a dozen people. The move angered al-Sadr's followers as well as Iraq's top Shiite cleric, Grand Ayatollah Ali al-Sistani (search), who said it violated a peace deal he brokered.

"This aggression is a serious precedent in the new Iraq and for the state which has thrown itself in the arms of the occupation," said sheik Hashim Abu Regheef in a sermon attended by hundreds of worshippers outside nearby Kufa Mosque.

U.S. and government forces "are trying to finish off this movement," he said.

Al-Sadr, who commands widespread support among Iraq's poorer Shiites, led a three-week uprising in Najaf against the U.S. Marines that ended last month with a peace deal brokered by al-Sistani.

"The pressures on us are great after the signing of the agreement," Regheef said. "We will be back if the leader orders us to ... We will rise up when we're ordered to."