The top UN human rights official today called for an international investigation into massacres and other crimes committed in Democratic Republic of Congo's Kasai region where at least 42 mass graves have been found.

The call sets up the possibility of a diplomatic confrontation between the United Nations and the government of President Joseph Kabila.

More than 600 primary and secondary schools have been damaged by attacks

The government had said it would accept UN technical assistance but wanted to retain control of the inquiry in response to a Thursday deadline by UN High Commissioner for Human Rights Zeid Ra'ad al-Hussein for Congo to agree to a joint probe.

But in his statement today, Zeid said the government "response to date falls short" and urged the UN Human Rights Council, which is holding a session until June 23, to act.

Government spokesman Lambert Mende told Reuters the government was not willing to go beyond its previous offer to run the investigation itself and accept UN technical help.

In the meantime, Unicef said today that tens of thousands of children are missing out on school amid violence between militia fighters and security forces and attacks against civilians.

The violence has kept at least 150,000 children in the region out of the classroom, while more than 600 primary and secondary schools have been damaged by attacks, Unicef said.

Some schools have been occupied by fighters, leaving pupils and teachers unwilling or unable to return, and others are being used as emergency shelter for families uprooted by the violence.

"Schools should be safe places where children can learn and begin to recover from the stress of the displacement or the memories of what they might have seen," said Tajudeen Oyewale, Unicef's acting representative in Congo.

"Returning to the classroom can give children a small sense of normality in troubled times," he said in a statement.

More than one in 10 children of primary school age in Greater Kasai have seen their education disrupted by violence, and many schools have been shut for several months, Unicef said.

Hundreds have been killed and 1.3 million displaced in central Congo since last August in fighting between a militia and government forces. Violence has risen nationally since Kabila decided to stay in power beyond the December 2016 end of his mandate.

"The international community is throwing its weight behind ensuring that the endemic impunity in the DRC is brought to an end," Zeid said.

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