The United Nations says it’s concerned at what it calls “disproportionate use of force” by Congolese forces as well as attacks by Kamwina Nsapu militia fighters during renewed violence in the Kananga region in the country’s southwest.

U.N. deputy spokesman Farhan Haq told reporters Monday that the U.N. peacekeeping mission in Congo expressed “grave concern” over reports of the fighting in Kananga, where it has received “credible reports of high numbers of deaths.”

A Congolese official said Saturday seven soldiers have been arrested following an online video that appeared to show men in Congolese uniforms fatally shooting more than a dozen alleged militia members armed with sticks.

Days earlier, the U.N. expressed grave concern about reports of more than 100 people killed during clashes between soldiers and militia fighters.