KINSHASA, Congo (AP) — The U.N. peacekeeping mission in Congo says at least 20 people have been killed as violence mounts in the country's center.

The mission, known as MONUSCO, released a statement Wednesday detailing the attacks in the Kasai provinces.

The region is where two U.N. experts — an American and a Swede — were slain along with their interpreter last month. A militia group known as Kamuina Nsapu filmed themselves killing the two and the footage circulated in the capital this week.

MONUSCO said there were at least 20 deaths in the town of Mungamba. The violence was blamed on ethnic tensions between the Lulua-Luba and Chokwe-Pende communities stoked by the militia fighters.

According to the U.N., at least 400 people have died since government troops killed the militia's leader in August.