Updated

A local official says a Congolese militia group has decapitated 42 policemen after ambushing them in Central Kasai province, which has seen a spike in deadly violence in recent months.

Kasai Assembly President Francois Kalamba said Saturday that members of the Kamwina Nsapu militia staged Friday's attack between the cities of Tshikapa and Kananga.

Kalamba says the militia members freed six policemen because they spoke the local Tshiluba language.

The Kamwina Nsapu militia has been fighting Congolese forces since August, when security forces killed their leader. The violence has left some 400 people dead. The U.N. and rights groups have warned Congo's military against excessive use of force.

Kasai Gov. Alexis Nkande Myopompa says investigations are underway into the decapitations.