The announcement by UN High Commissioner for Human Rights Zeid Ra'ad Al Hussein of the discovery of a further 17 mass graves in Kasai Central province in the Democratic Republic of Congo brings the number of such sites recorded by UN investigators to 40.

Fifteen of the newly uncovered graves were in a cemetery in the town of Tshimbulu, while two others were located in the village of Tshienke, according to the Office of the UN High Commissioner for Human Rights (OCHR).

Disproportionate force

Fighting erupted in Kasai last August after DR Congo government troops (FARDC) killed Jean Pierre Mpandi, leader of the Kamwina Nsapu militia, who had launched an uprising against President Joseph Kabila. The government troops are accused by the UN of using disproportionate force against Kamwina Nsapu, who are armed mostly with clubs and catapults. However, the UN also accuses the militia of recruiting child soldiers and committing atrocities.

The UN says the 17 newly discovered mass graves were reportedly dug by government troops following fighting with suspected militia members in March in which 74 people, including 30 children were killed.

The UN also said government troops reportedly killed at least 40 people in Kananga, capital of Kasai Central province, while going door-to-door looking for militia members. They reportedly buried an unknown number of bodies there.

The UN itself has also been targeted by the violence. Two UN researchers, who had been sent to the region to investigate it, were found in a grave 16 days after they were abducted last month.

Authorities announced on April 14 that two suspects had been detained over the kidnapping and killing of the two UN staff; an American and Swedish-Chilean woman. However, one of the suspects escaped with the help of four police officers who were guarding them.

It is against this background that Zeid, the UN human right chief, urged the government of the DR Congo to "take 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 right violations" in Kasai.

According to the website of the UN News Center, Zeid also warned the DR Congo government that if it didn't investigate the violence, he would "urge the international community to support an investigation by an international mechanism, including the International Criminal Court."

DR Congo's government spokesman Lambert Mende said they cannot be threatened like this by the UN and that the government had already shown it does not tolerate impunity. "Congo is not under the guardianship of the United Nations," he said.

Meanwhile Angola has said it is reinforcing security along its common border with DR Congo through which thousands of refugees have fled the fighting in Kasai.

Police chief Amborio de Lemos said on public RAN radio that "the Angolan police had intensified patrols on the border with the Democratic Republic of Congo to prevent the infiltration of armed groups."

So far 9,200 refugees have been registered in Angola. "All the Congolese refugees who are on our national territory are treated in a humane way," de Lemos said.