At least 303 civilians were raped by armed militia in the Democratic Republic of Congo (DRC) between July 30 and Aug. 2, according to a U.N. preliminary report released Friday.

"The known victims include 235 women, 52 girls, 13 men and three boys," said the report released by the U.N. Joint Human Rights Office based on its probe into the 13 affected villages in the Walikale region in Nordkivu province.

It also said the three armed militia groups involved looted at least 923 houses and 42 shops and kidnapped 116 civilians to use as forced labour, adding that the local Congolese army and police force had "serious shortcomings" in their ability to prevent such mass rapes.

These inabilities "to prevent or stop the attacks was compounded by subsequent failings on the part of MONUSCO forces (U.N. peacekeepers in DR Congo), which has not received any specific training on the protection of civilians, and suffered from a number of operational constraints," according to the report.

The three rebel groups were identified in the report as Mai-Mai Cheka group with about 200 members, the rebels of the Democratic Forces for the Liberation of Rwanda (FDLR) and a bloc involved with Emmanuel Nsengiyumva.

The report said the armed rebels came to the villages claiming they were their to protect them before launching attacks. While looting and raping, the militia also cut off all phone communications and trapped those who tried to flee.

Though the document admitted rape has been a perennial and mass problem in this part of the country for the past 15 years, "this incident stands out because of the extraordinarily cold-blooded and systematic way in which it appears to have been planned."