* Medical charity suspends work in Misrata detention centres
* Says its staff being asked to treat torture victims
* Allegations an embarrassment for Libya's new leaders
* Gov't official says takes serious view of torture (Adds government official, U.N. rights chief)
TRIPOLI, Jan 26 (Reuters) - Aid agency Medecins Sans Frontieres (MSF) has halted its work in detention centres in a Libyan city because it said its medical staff were being asked to patch up detainees mid-way through torture sessions so they could go back for more abuse.
Rights groups have repeatedly raised concerns about torture being used against people, many of them sub-Saharan Africans, suspected of having fought for Muammar Gaddafi's forces during Libya's nine-month civil war.
The agency said it was in Misrata, 200 km (130 miles) east of the Libyan capital and scene of some of the fiercest battles in the conflict, to treat war-wounded detainees but was instead having to treat fresh wounds from torture.
"Patients were brought to us in the middle of interrogation for medical care, in order to make them fit for more interrogation," MSF General Director Christopher Stokes said in a statement.
"This is unacceptable. Our role is to provide medical care to war casualties and sick detainees, not to repeatedly treat the same patients between torture sessions."
The agency said it has raised the issue with the authorities in Misrata and with the national army. "No action was taken," said Stokes. "We have therefore come to the decision to suspend our medical activities in the detention centres."
Reports of the mistreatment and disappearances of suspected Gaddafi loyalists are embarrassing for Libya's ruling National Transitional Council, which has vowed to make a break with practices under Gaddafi and respect human rights.
The allegations are also awkward for the Western powers which backed the anti-Gaddafi rebellion and helped install Libya's new leaders.
An official with the Libyan government said it paid attention to all credible reports of abuse.
"There is no doubt that there are acts of violation of human rights but these are to do with the mentality of the people who are in charge of these prisons," the official, who spoke on condition of anonymity, told Reuters.
"Neither the government, nor the NTC, nor any Libyan group supports these acts. These actions are individual acts and the authorities will take a very serious view of them."
DETAINEE "BEATEN AND WHIPPED"
B ut the ability of the government in Tripoli to rein in torture is limited because, in most cases, it is carried out by locally based militias who are outside the NTC's chain of command.
U.N. human rights chief Navi Pillay, speaking to the Security Council in New York on Wednesday, said that detainees from Libya's civil war held by revolutionary brigades continue to be subjected to torture despite efforts by the provisional government to address the issue.
Human rights group Amnesty International said on Thursday it had evidence of several detainees dying after being subjected to torture, including some in Misrata.
It quoted one man who said he had been tortured earlier this month in the headquarters of Misrata security forces.
"They took me for interrogation upstairs. Five men in plain clothes took turns beating and whipping me," Amnesty quoted the man as saying.
"They suspended me from the top of the door by my wrists for about an hour and kept beating me. They also kicked me."
The International Committee of the Red Cross said on Thursday that it has visited 8,500 detainees across Libya but declined to comment on the MSF decision to suspend its work. (Additional reporting by Stephanie Nebehay in Geneva; Writing by Christian Lowe; Edited by Diana Abdallah)