Three groups of armed militia could have committed crimes against humanity when they raped at least 387 people in the Democratic Republic of Congo in 2010, a UN probe said Wednesday. \"Due to the fact that these attacks were well-planned in advance and carried out in a systematic, targeted manner, they could constitute crimes against humanity and war crimes,\" investigators said in a report. The UN probe was set up to look into human rights violations committed between July 30 and August 2, 2010, in 13 villages in the Walikale territory of Nord Kivu. It blamed the rapes on members of the Mai-Mai Cheka group, the rebels of the Democratic Forces for the Liberation of Rwanda (FDLR) and a group connected to army deserter Emmanuel Nsengiyumva. Some 387 people fell victim to rape, including 300 women, 23 men, 55 girls and nine boys. In addition, at least 923 houses and 42 shops were looted. Another 116 civilians were abducted and subjected to forced labour. \"By using rape as a weapon of war, as a mean of terror and to ensure the enslavement of civilians, by planning, organising and attacking people in 13 villages along the Kibua-Mpofi axis,\" the armed militia coalition breached international law on the protection of civilians, said the investigators. The UN team noted that the leaders of the three armed groups did not directly participate in the rape. But this \"does not exempt them from criminal responsibility, as their prior knowledge of the plan of the attack, and their support... amount to strong evidence of their responsibility for the acts of violence committed by their subordinates,\" said investigators. The report also highlighted a persistent lack of accountability, as only one person Lieutenant Colonel Sadoke Kikonda Mayele of the Mai Mai Cheka has been arrested in connection with the case. A judicial inquiry into the violations was also suspended due to concerns over the safety of about 150 victims and witnesses interviewed, after some suffered reprisals. UN High Commissioner for Human Rights Navi Pillay stressed that this lack of progress in official investigations and action against perpetrators \"posed a severe obstacle to deterring future violations.\" \"Since the attacks in Walikale, there have been many other instances of rape and other types of sexual violence being systematically used as weapons of war and reprisal by armed groups,\" said Pillay. \"The government should pursue its efforts to bring perpetrators to justice and ensure that victims and witnesses are protected, given the high risk of reprisals,\" she said. Mass rape is a recurring problem in Democratic Republic of Congo, and not only rebels but also official troops count among perpetrators. Some 248 women reported that they were raped by soldiers in June in the Sud-Kivu province, a region that the UN has called the world\'s \"rape capital\".