Rioting inmates raped around 20 female prisoners during a failed prison break in Democratic Republic of Congo’s violence-ravaged east, the country’s U.N. peacekeeping mission said.

Two people were killed and 12 others were injured when prisoners detonated two grenades inside the central prison in Goma, capital of the eastern border province of North Kivu, during an overnight escape attempt that began late on Sunday.

“The group of mutinying soldiers ... raped around 20 female inmates,” said the statement released late on Monday by the U.N. mission, known as MONUC.