KINSHASA, Congo (AP) — Authorities say a brutal armed group in southern Congo blamed for murdering a U.N. team has killed at least eight people over the weekend.

The fighters loyal to traditional leader Kamwina Nsapu launched their attack on Luebo late Friday. Among the victims was the area administrator's wife.

Joseph Mbuyi Mubenga said after killing his wife, the fighters mutilated her body, decapitating her and taking her head, hands and feet.

Mubenga told U.N.-backed Radio Okapi that the attackers also set fire to administrative buildings including the prison as well as a local convent of nuns.

Violence is mounting in three neighboring provinces in southern Congo, where more than 400 civilians have been killed since August including two U.N. experts and their interpreter. Three others working with that team remain missing.