Amnesty International said that despite promises, Libya’s new rulers have made “no progress to stop the use of torture”, as Doctors Without Borders suspended its work in the third-largest city of Misrata over similar claims.

Their accusations come after a top UN official raised concerns that armed militias comprising former rebels who helped topple Kadhafi were posing increasing security risk as they regularly clashed with each other.

“Several detainees have died after being subjected to torture in Libya in recent weeks and months amid widespread torture and ill-treatment of suspected pro-Kadhafi fighters and loyalists,” Amnesty said in a statement.

It said its delegates met detainees held in Tripoli, in Misrata and in smaller towns such as Ghariyan who showed visible signs of torture inflicted in recent days and weeks.

“The torture is being carried out by officially recognised military and security entities, as well by a multitude of armed militias operating outside any legal framework,” it said.

Donatella Rouvera, senior adviser at London-based Amnesty, said in the statement that it was “horrifying to find that there has been no progress to stop the use of torture”.

“We are not aware of any proper investigations into cases of torture,” she said.

Detainees told Amnesty they had been beaten for hours with whips, cables, plastic hoses, metal chains, bars, wooden sticks and given electric shocks with live wires.

The rights watchdog said the detainees, both Libyans and foreigners from sub-Saharan Africa, were tortured soon after they were seized by armed militias in officially recognised detention centres in places like Misrata.

Misrata withstood a devastating siege by Kadhafi’s forces during last year’s uprising. Its fighters later unleashed a fierce attack on the dictator’s hometown of Sirte, where he was killed on October 20.

“Several detainees have died in the custody of armed militias in and around Tripoli and Misrata in circumstances that suggest torture,” Amnesty added.

Rouvera said the issue was aggravated as the police and judiciary remained “dysfunctional” cross Libya.

Doctors Without Borders, meanwhile, said it has suspended its work in Misrata.

“Detainees in the Libyan city of Misrata are being tortured and denied urgent medical care, leading the international medical humanitarian organisation Medecins Sans Frontieres (MSF) to suspend its operations in detention centres in Misrata,” the group said, referring to itself by its French name.

It said its doctors were increasingly confronted with patients who suffered injuries caused by “torture” during questioning.

“The interrogations were held outside the detention centres,” it said.

MSF general director Christopher Stokes said some officials have sought to exploit and obstruct its work in Misrata.

“Patients were brought to us in the middle of interrogation for medical care, in order to make them fit for further interrogation. This is unacceptable,” he said.

“Our role is to provide medical care to war casualties and sick detainees, not to repeatedly treat the same patients between torture sessions.”

On Wednesday, the UN special representative in Libya, Ian Martin, expressed concern about the militias which he said were not under the control of the interim government.

Speaking to the UN Security Council, Martin said fighting in the Libyan town of Bani Walid this week — at one stage blamed on Kadhafi loyalists — had been caused by a clash between local people and a revolutionary brigade unit.

“Although authorities have successfully contained these and other more minor incidents that continue to take place across the country on a regular basis, there is the ever present possibility that similar outbreaks of violence could escalate,” he said.

Libya’s new authorities are struggling to reintegrate tens of thousands of these militia fighters into the army and police.