The United Nations top anti-torture body told the United States that any secret jails it ran for foreign terrorism suspects, along with the Guantanamo Bay facility, were illegal and should be closed.
In its first review of US policy since Washington launched its war on terrorism, the Committee against Torture also urged President George W. Bush to ban interrogation methods that could be regarded as torture or cruel treatment.
It cited use of dogs to terrify detainees, "water-boarding" which is a form of mock drowning, and sexual humiliation, saying that some detainees had died during questioning.
The US State Department rejected the recommendations to close detention facilities as being beyond the committee's anti-torture mandate.
The group of 10 independent experts, who have moral authority but no legal power to enforce recommendations, said the United States "should ensure that no one is detained in any secret detention facility under its de facto effective control".
"Detaining persons in such conditions constitutes, per se, a violation of the Convention," said the body which examines compliance with the 1987 UN Convention against Torture or other Cruel, Inhuman or Degrading Treatment or Punishment.
The United States openly holds hundreds of terrorism suspects, most arrested since al Qaeda's September 11 attacks, at its prisons in Afghanistan, Iraq and Guantanamo Bay, Cuba.
The UN committee voiced concern at "reliable reports of acts of torture or cruel, inhuman and degrading treatment" by US military or civilian personnel.