A US defense contractor accused of helping torture prisoners at Iraq's infamous Abu Ghraib prison has paid former detainees more than $5 million to settle a lawsuit, according to regulatory filings obtained by AFP on Wednesday.

Iraqi officials said they believed this was the first American payment in connection with torture at Abu Ghraib.

The prison shot to international headlines after the publication in 2004 of photographs showing Iraqi detainees being humiliated and abused by their US guards in the aftermath of the 2003 invasion.

The plaintiffs, 72 former detainees, alleged that L-3 Services Inc. (now called Engility Holdings) and others, "either participated in, approved of, or condoned the mistreatment of prisoners by United States military officials," according to the document.

"On October 5, 2012, we and the plaintiffs agreed to resolve and dismiss the action in return for a payment of $5.28 million," the company wrote in its third quarter report to the Securities and Exchange Commission.

Iraqi human rights ministry spokesman Kamil al-Amin told AFP that officials believed the payment marked "the first time that the Americans have given anything for prisoners tortured at Abu Ghraib."

Another government official who requested anonymity went further, saying they thought it was the first time any payment had been made in connection with Abu Ghraib.

The prison west of Baghdad became a potent negative symbol of the US occupation to many Iraqis after evidence emerged of detainee abuse by American soldiers at the facility.

The scandal led to the sentencing of 11 soldiers to up to 10 years in prison.

The majority of the abuse took place at the end of 2003, when employees of L-3 and contracting firm CACI were working in the prison, US military courts have said.

The initial complaint was originally filed on May 5, 2008, the company stated, adding that multiple cases were consolidated into a single lawsuit to be heard in federal court in Maryland.

It said it agreed to settle after first losing a motion to dismiss the complaint in 2010, and an appeal of that decision in 2012.

L-3 employed translators at Abu Ghraib in 2003, according to the lawsuit, which also named CACI International Inc and CACI Premier Technology for providing interrogators to the detention centre.

Lawyers representing the defendants said they were subjected to months of abuse while being held at the jail.

One of the detainees, Emad Al-Janabi, was subjected to physical and mental torture which included being shown a mock execution of his brother and nephew, being repeatedly deprived of food and sleep and threatened with dogs, according to the lawsuit.

He was later released without charge in July 2004 after being held since the previous September.

Abu Ghraib also served as a torture centre under executed dictator Saddam Hussein's ousted regime, with an estimated 4,000 detainees losing their lives there.