US forces in Iraq have released a close aide to Muqtada al-Sadr, the Shia cleric who led uprisings against US troops last year, officials in al-Sadr's organisation say. Mohammed al-Tabtabaei had spent a year in detention at Abu Ghraib prison in Baghdad, but was freed without charge, they said. He was detained during the first of two uprisings mounted last year by al-Sadr across southern Iraq. The US military confirmed his release. Al-Sadr himself faces an arrest warrant for murder issued under the US occupation authority in 2003. But he has been largely left alone by the Iraqi authorities since he agreed to disband his al-Mahdi Army following fighting last August.