GENEVA — The top United Nations human rights official on Tuesday accused a militia linked to the government of the Democratic Republic of Congo of atrocities, including mass killings, pregnant women cut open and infants hacked with machetes.

The Bana Mura militia “have in the past two months shot dead, hacked or burned to death and mutilated hundreds of villagers, as well as destroying entire villages” in the central Kasaï region, the official, Zeid Ra’ad al-Hussein, told the Human Rights Council in Geneva.

The large scale and horrific nature of the crimes necessitated an independent international investigation, Mr. al-Hussein, the high commissioner for human rights, told diplomats in the council.

In a report that reinforced the United Nations assessment, the Catholic Church in Congo said on Tuesday that 3,383 people had died in violence in the region since October, and that 20 villages had been destroyed, 10 of them by the Congolese Army.