The US military said it released some 230 detainees on Thursday from Baghdad's notorious Abu Ghraib prison and the coalition's other major detention facility of Camp Bucca in the southern town of Umm Qasr.
"We have released a total of around 230 detainees today, the majority of them from Camp Bucca," Lieutenant Colonel Barry Johnson told AFP.
Sheikh Hisham Dulaimi, a tribal chief heading an association for the defence of prisoners' rights, had said earlier the military freed 74 Iraqis from Abu Ghraib.
They were bused out of the infamous prison under US military escort and dropped off at an Iraqi national guard base in the Amiriyah neighbourhood on the western outskirts of the capital, he said.
Among those freed from Camp Bucca after almost a year of detention was Sheikh Moayad al-Khazraji, an aide to Moqtada Sadr, according to one of his friends.
Johnson said the latest releases raised to just over 800 the number of prisoners released since August, when a joint release board which includes six Iraqi officials and three veto-holding coalition officials was set up.