A U.S. civil rights group said it has obtained documents from the defense department that confirm the U.S. ignored the use of torture by special forces in the interrogation of Afghani prisoners.

A lawyer with the American Civil Liberties Union said "These documents make it clear that the military was using unlawful interrogation techniques in Afghanistan. Rather than putting a stop to these systemic abuses, senior officials appear to have turned a blind eye to them."

U.S. Special Forces officers admitted employing special interrogation methods, which included beating, burning and using extreme cold, on eight prisoners at Gardez prison in Afghanistan.

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The use of the special interrogation techniques came to light during a criminal investigation into the death in March 2003 of an Afghani prisoner, Jamal Naseer, who died at Gardez in U.S. custody.

The investigation stated that Naseer died of a "stomach ailment," although no post mortem was carried out to confirm the cause of death. There were also a number of statements from witnesses alleging torture and abusive practices, however, the investigation concluded the evidence was "unsupported."

"These documents raise serious questions about the adequacy of the military's investigations into prisoner abuse," Amrit Singh from the ACLU said.

The Survival, Evasion, Resistance and Escape (SERE) techniques have been used for decades by the U.S. in military training to prepare American personnel for capture by enemy forces.

Scandals surrounding the United States' treatment of prisoners in Iraq, Guantanamo Bay and Afghanistan have drawn widespread condemnation from the international community.

In 2004 photographs of abuse by U.S. military personnel at Abu Ghraib prison, in Iraq, were shown on American television and in papers all over the world.

The images led to a criminal investigation and the conviction and subsequent imprisonment of a number of U.S. personnel, the head of the prison was demoted.

However, U.S. personnel claimed that high-ranking U.S. officials sanctioned the interrogation methods which involved military intelligence, although a Senate panel on Abu Ghraib was told there were no "direct" or written orders authorizing the abuse of prisoners.