KABUL, Aug 21: A UN human rights expert on Saturday slammed US military authorities in Afghanistan for barring him from visiting detention centres and pronounced a Kabul prison "inhuman".

Cherif Bassiouni said: "The lack of giving an opportunity for people to go and see these facilities is a lack of transparency that raises serious concerns about the legality of detention...and conditions of those detainees."

Former prisoners say they were tortured and abused while in US custody, raising concerns that scandal over the mistreatment of prisoners at Iraq's Abu Ghraib prison earlier this year was not an isolated episode.

The US military, which had earlier this month been expected to release an internal report into allegations of prisoner abuse, turned down his request to visit centres where suspected militants are held.

Bassiouni was allowed to visit Kabul's notorious Pul-i-Charkhi jail, run by the Afghan authorities, where some 725 members of the Taliban are being held.

Mr Bassiouni pronounced conditions there "inhuman" and said the prisoners should be freed.

"These persons should be released immediately. There is no legal, human or even political justification to keep them," he said. But added that at least he had been allowed in to see the prison.

The rights controversy was stirred by the arrest of three US citizens in Kabul in early July for illegally detaining and torturing Afghans.

The leader of a vigilante group, Jonathan "Jack" Idema said no torture was used during interrogations and his group colluded with US security agencies as well as the Department of Defence. The US authorities have denied any link with Idema's group.

The UN rights expert has been in Afghanistan for a week and said the country had made progress in the past two years but went on to list violations ranging from execution, torture, arbitrary arrest, detention, seizure of private property and crimes against humanity. He said these violations were "committed by state and non-state actors as part of a widespread or systematic policies".-Reuters