The Pentagon sent an officer who advised murderous forces in 1980s Central America to oversee Iraqi police units that ran secret detention and torture centers while Gen. David Petraeus was in charge there, the British newspaper the Guardian and the BBC reported Wednesday.

“These units conducted some of the worst acts of torture during the U.S. occupation and accelerated the country's descent into full-scale civil war,” the paper states.

Retired Col. James Steele was a special forces veteran when he was sent by then-U.S. Defense Secretary Donald Rumsfeld to help organize Shi’a paramilitaries in an attempt to quell the Sunni insurgency, according to the report.

After the Pentagon lifted a ban on Shi’a militias joining the security forces, the membership of the special police commandos was increasingly drawn from extremist, Iran-backed Shi’a groups like the Badr brigades.

A second special adviser, retired Col. James Coffman, worked with Steele in the U.S.-funded prisons, the report states. Coffman reported to Petraeus, who sent to Iraq in 2004 to organize and train the new Iraqi security forces. Steele, who was in Iraq from 2003 through 2005, and kept returning to the country through 2006, reported directly to Rumsfeld.

The allegations made by both American and Iraqi witnesses in the Guardian/BBC documentary for the first time implicates U.S. advisers in the human rights abuses committed by the commandos. It is also the first time Petraeus – who last November was forced to resign as director of the CIA  in sex scandal – has been linked through an adviser to this abuse.

"They worked hand in hand," Iraqi Gen. Muntadher al-Samari, who worked with Steele and Coffman while the commandos were being set up, told the news outlets. "I never saw them apart in the 40 or 50 times I saw them inside the detention centers. They knew everything that was going on there ... the torture, the most horrible kinds of torture."

The pattern in Iraq shadows the well-documented atrocities committed by U.S.-advised and -funded paramilitary squads in Central America in the 1980s. Steele was head of a U.S. team that trained units of El Salvador security forces in counterinsurgency. Petraeus visited El Salvador in 1986 while Steele was there and became a major advocate of counterinsurgency methods.

Steele and Coffman have declined comment on the damning report. Steele has in the past denied any involvement in torture.

A spokesman for Petraeus told the BBC/Guardian investigation: "During the course of his years in Iraq, General Petraeus did learn of allegations of Iraqi forces torturing detainees. In each incident, he shared information immediately with the U.S. military chain of command, the U.S. ambassador in Baghdad ... and the relevant Iraqi leaders."

The Guardian says the investigation was sparked by the release of classified U.S. military logs on WikiLeaks that detailed numerous incidents where U.S. soldiers came across tortured detainees in a network of detention centers run by the Iraqi police. Pvt. Bradley Manning is facing a prison sentence of up to 20 years after he pleaded guilty to leaking the documents.