Former U.S. Army reservist Charles A. Graner Jr. poses next to an Iraqi detainee who died during interrogation in late 2003 at the Abu Ghraib prison in Baghdad, Iraq, in a series of photographs that triggered international outrage over the treatment of prisoners in U.S. military custody. Associated Press

The alleged ringleader of detainee abuses at Abu Ghraib in Iraq was released Saturday from a U.S. military prison, according to an army spokeswoman.

Charles Graner Jr., 42, was released from the U.S. Disciplinary Barracks at Fort Leavenworth, Kansas, after serving more than 6 1/2 years of a 10-year sentence, spokeswoman Rebecca Steed said. Graner will be under the supervision of a probation officer until Dec. 25, 2014, she said.

Graner was an Army Reserve corporal when he and six other members of the Maryland-based 372nd Military Police Company were charged in 2004 with abusing detainees at the prison in Iraq. The strongest evidence was photographs of grinning U.S. soldiers posing beside naked detainees stacked in a pyramid or held on a leash.

The pictures complicated international relations for the U.S. and provoked debate about whether harsh interrogation techniques approved by the Pentagon amounted to torture.

Steed said she could not release any information about Graner's whereabouts or his destination after release. Neither Graner nor his wife have responded to interview requests from The Associated Press.

Reservist claimed abuse sanctioned by military

Graner was convicted of offences that included stacking the prisoners into a pyramid, knocking one of them out with a head punch and ordering prisoners to masturbate while soldiers took pictures.

He maintained that the actions were part of a plan directed by military intelligence officers to soften up prisoners for interrogation.

Graner, who received the longest sentence, is the last Abu Ghraib defendant to be released from prison. Calls and emails to Graner's father and lawyer were not immediately returned.

During his deployment, Graner fathered a son with former Pfc. Lynndie England. England was given a three-year sentence for her role in the scandal.

After his conviction, Graner married another member of his unit, former Spc. Megan Ambuhl. She was discharged from the Army after pleading guilty to dereliction of duty for failing to prevent or report the maltreatment.