Established in 2003 as a holding facility for security detainees near Baghdad International Airport, the prison had the capacity to hold up to 4,000 detainees.

With this handover, the U.S. military's oversight on detainee operations significantly diminishes, a cause of concern for Iraqis who largely don't trust their justice system.

The United States will continue to have advisers and special teams inspect facilities if there are reports of torture and abuse.

Military commanders said that the Iraqis were trained to international standards.

"We will also continue to be involved with advisers and in accordance with the security agreement we have every expectation that we will be able to continue to do checks and balances that are presented to us when there is a problem situation," said Maj. Gen. Jerry Cannon, deputy commanding general for detainee operations.