UN says 17 mass graves found in DR Congo
Fighting erupted in Kasai after government troops last August killed tribal chief Jean Pierre Mpandi, also known as Kamwina Nsapu, who had launched an uprising against President Joseph Kabila.
Wednesday's announcement by UN rights chief Zeid Ra'ad Al Hussein raises to 40 the number of mass graves discovered in Kasai.
Fifteen of the newly uncovered graves were in a cemetery in the town of Tshimbulu, with two others in the village of Tshienke, the rights office said in a statement.
The latest discoveries "highlight the horror" that has gripped the area over the last nine months, Zeid said.
Two United Nations researchers, who had been sent to investigate violence in the region, were found in a grave 16 days after they were abducted last month.
"It is absolutely vital that the government of the DRC takes meaningful steps, which to date have been lacking, to ensure that there is a prompt, transparent, and independent investigation to establish the facts and circumstances of alleged human rights violations and abuses," Zeid said of the Kasai violence.
If the government does not take such action, Zeid said he would "not hesitate to urge the international community to support an investigation by an international mechanism, including the International Criminal Court".
Authorities announced on April 14 that two suspects had been detained over the kidnap and killing of the two UN experts, an American and a dual Swedish-Chilean woman.
One of the suspects, however, escaped with the help of four police officers guarding them.
DR Congo security forces have been accused by the UN of using disproportionate force against militiamen, who are armed mainly with clubs and catapults.
However, the UN also accuses the rebels of recruiting child soldiers and of committing widespread atrocities.