Iraqis on Sunday expressed anger at the release of the ringleader of US guards who abused detainees at Abu Ghraib prison, and said US troops should not be granted further immunity from Iraqi prosecution.

Charles Graner, 42, was on Saturday freed on parole from the US Disciplinary Barracks at Fort Leavenworth, Kansas after serving over six and a half years of a 10-year sentence, US army spokeswoman Rebecca Steed told AFP, saying he was released early for good conduct and through work rehabilitation programmes.

In Baghdad, residents slammed the decision and said they opposed the extension of immunity from Iraqi justice for any US soldiers who remain in the country on a training mission being discussed for after the end of this year -- a condition insisted upon by American officials.

"This is an unjust decision," said Wael Safah Jassem, a 23-year-old shop-owner with close-cropped hair. "Anyone who committed such crimes should not be freed" so easily.

He added that if US troops remain in Iraq past the end of the year, "it is wrong for them to have immunity."

Iraqi leaders have agreed to talks with the United States on a possible extension of its troop presence, but a decision has not yet been made.

US troops have had immunity under Iraqi law since the 2003 invasion that toppled Saddam Hussein, leaving soldiers such as Graner and others who have committed abuses or even murder subject only to US prosecution.

"The criminal who was released ... should be brought to an Iraqi court to be judged," said Anwar Hamud, a 41-year-old government employee with a bushy moustache, who gestured angrily as he spoke.

"He should be executed for his crime in Abu Ghraib," he said.

"They should not have any immunity," he said when asked about the possible extension of the policy for US troops. "If we give them immunity, that means nothing has changed; they will commit other crimes."

"The immunity in Iraq should be cancelled, as should their presence here," he said. "Iraq should have full sovereignty."

Graner led a six-member team of prison guards who sexually humiliated naked prisoners at the Abu Ghraib prison outside Baghdad in a scandal that dealt a severe blow to the US's reputation after it came to light in 2004.

Photographs taken by the guards and obtained by the media showed US soldiers grinning as they posed next to detainees held on a leash or stacked in a pyramid.

Others showed the detainees forced into stress positions, their heads covered in a black hood, or being threatened by attack dogs.

"Why did they release him? The criminal should be punished," regardless of his nationality, said Reem Hadi, who has worked as a teacher but said she has been unsuccessfully trying to find a job for years.

"We reject immunity being given to US soldiers if they stay," said the 42-year-old, who wore a tan hijab and sunglasses, adding "many people were hurt because of that immunity."

"They have immunity, and they are killing and arresting everywhere -- is that just?" she asked. "Would US citizens accept such things?"

"I don't want them to stay any more."