Two US human rights groups sued Defence Secretary Donald Rumsfeld on Tuesday, saying he first authorized and then failed to stop torture of prisoners in Iraq and Afghanistan.

The American Civil Liberties Union and Human Rights First filed suit in federal district court in Rumsfeld's home state of Illinois on behalf of eight former detainees who said they were severely tortured. All eight were subsequently released without being charged.

"Secretary Rumsfeld bears direct and ultimate responsibility for this descent into horror by personally authorizing unlawful interrogation techniques and by abdicating his legal duty to stop torture," said Lucas Guttentag, lead counsel in the case.

The Pentagon denied that it ever sanctioned or condoned the abuse of detainees.

"There have been multiple investigations into the various aspects of detainee abuse. None have concluded there was a policy of abuse," the Defence Department said in a statement.

The ACLU filed similar complaints against three other senior officers: Col. Thomas Pappas, Gen. Janis Karpinski and Lt. Gen. Ricardo Sanchez on behalf of prisoners mistreated at Iraq's Abu Ghraib prison.