The United Nations estimates at least 400 people have been killed and around one million people have been forced to flee since last July when the militia first launched an uprising.
Congo's government is under pressure to investigate the violence in Kasai, where the United Nations says it has found a total of 40 mass grave sites it says may need to be probed by the International Criminal Court if the government fails to. Several Congolese officials close to President Joseph Kabila are subject to Western sanctions for police brutality -- allegations which Congo regularly denies. Tensions with the West are also high due to criticism of Kabila, whose mandate to rule the country of 70 million people expired in December 2016.
The U.N. on Monday criticized Congolese authorities for releasing a video showing the grisly murders of two U.N. experts, saying the move could harm the investigation and was traumatic for the families. "The video is evidence in the crime. We don't think it should have been released. We don't think it should have been shown," said UN spokesman Stephane Dujarric. Two suspects were detained over the kidnap and murder of Sharp, who was American, and dual Swedish-Chilean national Catalan, earlier this month, but one escaped with the help of police guarding them. Sharp and Catalan were members of the UN panel of experts who were seeking to investigate reports of mass graves in the central Kasai region.