“These crimes, many of which could constitute war crimes and crimes against humanity can be attributed to the former Seleka coalition and the Antibalaka,” said the UN statement on Tuesday.
In a report at the start of this month, Human Rights Watch blamed the FPRC rebel group for killing at least 11 civilians on August 25, who fled Bria after clashes between the FDRC and the Antibalaka.
Several rebel groups and militias are fighting in Bria, which is home to some 100,000 people, for control over the diamond mines.
France, the former colonial power, intervened to remove the Seleka after the 2013 unrest following Bozize’s ouster and the UN deployed a peacekeeping mission named Minusca in 2014. The UN stabilisation force in Central Africa has 11,000 troops and 2,000 police officers.