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 UN-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 UN experts and their interpreter.
Disclaimer: No Business Standard Journalist was involved in creation of this content