Human Rights First, formerly known as the Lawyers Committee for Human Rights, said in a report that secrecy surrounding these facilities made "inappropriate detention and abuse not only likely but inevitable."

"The abuses at Guantanamo Bay and Abu Ghraib cannot be addressed in isolation," said Deborah Pearlstein, director of the group's US Law and Security program, referring to the US Naval base prison in Cuba and Abu Ghraib prison in Iraq where abuses are being investigated.

"This is all about secrecy, accountability and the law," Pearlstein told a news conference.

The report coincided with news that Defence Secretary Donald Rumsfeld ordered military officials to hold a suspect in a prison near Baghdad without telling the Red Cross. Pearlstein said this would be a violation of the Geneva Conventions and Defence Department directives.

She said thousands of security detainees were being held by the United States in Iraq and Afghanistan as well as locations elsewhere which the military refused to disclose.

"The US government is holding prisoners in a secret system of off-shore prisons beyond the reach of adequate supervision, accountability of law," said the report.

Pearlstein said multiple sources reported US detention centers in, among other places, Kohat in Pakistan near the border with Afghanistan, on the Indian Ocean island of Diego Garcia and at Al Jafr prison in Jordan, where the group said the CIA had an interrogation facility.

Prisoners are also being held at the Naval Consolidated Brig in Charleston, South Carolina, and others were suspected of being held on US warships.

A defence department spokesman told Reuters he would comment when he had more information about the report.

Pearlstein called for the US authorities to end "secret detentions," provide a list of prisoners, investigate abuses and allow the International Committee of the Red Cross unfettered access to detainees.