Doctors Without Borders has suspended its work in prisons in the Libyan city of Misrata because it said torture was so rampant that some detainees were brought for care only to make them fit for further interrogation, the group said Thursday.

The announcement was compounded by a statement from Amnesty International saying it has recorded widespread prisoner abuse in other cities as well, leading to the death of several inmates.

The allegations, which come more than three months after former leader Moammar Gadhafi was captured and killed, were an embarrassment to the governing National Transitional Council, which is struggling to establish its authority in the divided nation.

Doctors Without Borders said that since August, its medical teams have treated 115 people in Misrata who bore torture-related wounds, including cigarette burns, heavy bruising, bone fractures, tissue burns from electric shocks and kidney failure from beatings. Two detainees died after being interrogated, the group's general director said.

"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," MSF general director Christopher Stokes said in a statement. "Our role is to provide medical care to war casualties and sick detainees, not to repeatedly treat the same patients between torture sessions."

Libya's Western-backed leadership, which has sought to assure the world of its commitment to democracy and human rights, has acknowledged that some prisoners held by revolutionary forces have been abused. It insisted the mistreatment was not systematic and pledged to tackle the problem.

But the transitional government has been unable to rein in the dozens of militias that arose during the war and have been reluctant to disband or submit to central authority.

Amnesty International said in a statement issued Thursday that it has met with a number of detainees in Tripoli, Misrata, and Gharyan who showed visible marks indicating torture, including open wounds on the head, limbs, back and other parts of the body. A number of detainees spoke to Amnesty about beatings with electric cables and metal chains, and they reported being suspended in contorted positions and given electric shocks.

The London-based group said the torture and mistreatment, mostly against suspected Gadhafi loyalists and sometimes foreign nationals from sub-Saharan African countries, is carried out by officially recognized military and security bodies as well as by a number of armed militias operating outside any legal framework. The group said several detainees died in custody from torture, detailing the death of at least two detainees.

Britain, which played a key role in the NATO-led air campaign that helped revolutionary forces overthrow Gadhafi, urged the new regime to "live up to the high standards they have set themselves."

"They need to ensure a zero tolerance policy on abuse. We are concerned about these reports and are taking them up with the Libyans as a matter of urgency," British Prime Minister David Cameron's office said in a statement.

The head of Amnesty International told The Associated Press the mistreatment of detainees in Libya showed the need for the international community to keep helping the country in its difficult transition. "It's not just a matter of sending in troops and then getting out again. Libya needs long term assistance," Salil Shetty said.

Stokes, of the MSF, told The Associated Press that those subjected to torture include ex-combatants and people accused of theft and looting.

"There is a significant number of people with darker skin, but there is really a wide mix," he said. "Whatever the motives, it is unacceptable to do this to human beings."

The interrogations were carried out by Libya's National Army Security Service at facilities outside the detention centers, MSF said in a statement.

The group, which operates in prisons but not interrogation centers, said it contacted authorities in Misrata, the port city that saw some of the fiercest fighting of the war, to demand an end to the abuse, but it received no official response, prompting MSF to halt its operations in the city's detention centers.

MSF said it will continue its support in Misrata hospitals and schools in addition to providing assistance to African migrants, refugees and internally displaced people in and around Tripoli.

In its statement, MSF said the most alarming case was on Jan. 3, when MSF doctors treated a group of 14 detainees returning from an interrogation center. It said nine of the detainees had numerous injuries, including broken arms and renal failure, and displayed obvious signs of torture.

Stokes said his group has informed the National Army Security Service that a number of patients needed to be transferred to hospitals for urgent and specialized care. All but one of the detainees were deprived of further medical care and hospitalization, and instead taken back to interrogation centers.

"Some of them couldn't even stand up, they were so badly beaten," he said.

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El Deeb reported from Cairo. Associated Press writer Frank Jordans in Geneva contributed to this report.