United Nations investigators, working together with Congolese military investigators, have identified an additional 38 mass graves in six different locations in the western Kasai region.
This brings the mass graves total to nearly 80 since last August.
The head of UN peacekeeping Jean-Pierre Lacroix has warned violence in the region has reached “very disturbing levels.”
Investigators have already found dozens of mass graves over the last year, since fighting began between the military and the Kamuina Nsapu militia. The insurgents are fighting to force government troops out of the Kasai region.
The Congolese government blames the rebels for the mass graves, but witnesses interviewed by Reuters news agency in March said they have seen government army trucks dumping bodies.
The UN has previously accused the military of excessive force – a claim the government denies.
The UN estimates around 3,300 people have been killed since the start of the insurrection, and a further 1.4 million people have been forced to flee the area due to the violence.
Earlier this week, the Congolese government confirmed that the country’s long-delayed election would not be held before the end of 2017.
President Joseph Kabila’s second term ended last December, and the government and opposition had agreed a deal which would have seen elections held by December 31st this year.