A UN inquiry report said that inmates were routinely forced to take off their clothes in secret CIA detention facilities in Afghanistan.
The report also said that many prisoners are denied access to lawyers and deprived of the right to visit their relatives.
The developments came as a well-known Afghan prisoner named Shir Khan has said Washington still runs secret jails in Afghanistan despite US President Barack Obama’s claim to the contrary.
Khan said the inmates were blindfolded, hanged from the ceiling and dogs were unleashed on them during interrogation.
Several reports have confirmed that American jail guards have mistreated Afghan detainees held at the notorious US-run Bagram prison camp and airbase in Afghanistan.
The International Committee of the Red Cross (ICRC) said in May 2010 that it had been informed of the names of several detainees held in the secret prison in Afghanistan.
A number of former inmates of the main US military base at Bagram said they were abused and isolated during detention there.
Human rights groups said that Bagram has remained a US torture cell since the toppling of the Taliban regime in Afghanistan nine years ago.
US officials, however, claimed that all inmates in the facility were treated humanely.