Around 150 prisoners were recaptured after the break from a detention center near Lubumbashi. Of those who remain at large, the U.N. peacekeeping mission in the DRC, MONUSCO, said it was concerned about the whereabouts of Gedeon Kyungu Mutanga, a former leader of the Mai Mai militia.
"National authorities are currently searching for him and have launched a manhunt," MONUSCO spokesman Madnodje Mounabai said in a statement.
Witness accounts said armed members of the Democratic Forces for the Liberation of Rwanda, or FDLR, and the Mai Mai militia were behind widespread sexual violence in DRC. The FDLR is linked to the Rwandan genocide in 1994.
The trouble comes as DRC gears up for presidential elections in November.
Incumbent President Joseph Kabila will likely square off against rivals including the country's former House Speaker Vital Kamerhe.
Armed supporters of Kabila's People's Party for Reconstruction and Democracy stormed the Kinshasa headquarters of the opposition Union for Democracy and Social Progress this week, adding to the list of MONUSCO's concerns.