By Mark John BRUSSELS, Nov 12 (Reuters) - Amnesty International urged NATO troops in Afghanistan on Monday to suspend all transfers of detainees to Afghan authorities, citing persistent allegations that prisoners face torture. The rights group said dozens of prisoners taken by the NATO-led International Security Assistance Force (ISAF) had been handed over to Afghanistan's intelligence services, the National Directorate of Security (NDS), despite such allegations. "Amnesty International is concerned that ISAF states are breaching their international obligations by handing over detainees to the NDS, where detainees are at grave risk of torture and ill-treatment," it said in a report. International conventions prohibit transfers of prisoners if there is reason to suspect abuse and some rights experts say Western troops could face prosecution in such cases. ISAF nations including Britain, the Netherlands, Denmark and Canada have memorandums of understanding with Afghan authorities that detainees be treated according to international standards, but Amnesty said adequately monitoring the pacts was impossible. "While...the agreements may seek to ensure that detainees are not tortured or otherwise ill-treated, they have failed to do so," it concluded, arguing that some areas of Afghanistan were not accessible to independent monitors. It urged NATO's 40,000-strong ISAF to suspend transfers of detainees to Afghan authorities and use the time to back prison reform and training of penitentiary personnel alongside bodies such as the European Union. NATO dismissed Amnesty's proposal for a transfer moratorium: "Our policy was developed with the Red Cross/Crescent and meets international standards. We are comfortable with it," NATO spokesman James Appathurai said. "NATO-ISAF has no evidence of mistreatment of detainees transferred by NATO to Afghan custody. Of course we could never rule it out, but we part ways with Amnesty on the way forward ...It is not for NATO to create a parallel detention system." There was no immediate comment from the Afghan government. Amnesty said Britain had confirmed to its researchers that it was checking an allegation of torture or ill-treatment of a transferred Afghan detainee this September, while Belgium had acknowledged losing track of a suspect suicide bomber arrested in Kabul in April and subsequently transferred to the NDS. Amnesty quoted an email it said was sent in April by Norway's Kabul embassy to the Norwegian foreign ministry raising concerns about alleged torture of several detainees by the NDS. NATO has been particularly anxious to defend its policy on detentions since the 26-member alliance last year moved into the south of Afghanistan, where battles against Taliban and other insurgents are at their toughest. Canada last month rejected allegations Taliban members captured by its troops and handed over to Afghan authorities had been tortured, saying militants often made false claims. (Additional reporting by Jon Hemming in Kabul, Editing by Matthew Jones)