The massacre took place over three days in December, not long before the country's long-delayed presidential election. Violence erupted in Yumbi between the Banunu and Batende communities after a dispute over a burial for a Banunu customary chief.
The attacks "followed strikingly similar patterns and were characterized by extreme violence and speed, leaving little time for people to escape," the U.N. said. Banunu villagers were targeted with weapons including firearms and gasoline, the investigation found.
The death toll is likely to be higher because victims' bodies are believed to have been dumped in the nearby Congo River, the U.N. said. "The similarity in the way the attacks were carried out indicated prior consultation and organization," the report said. "Certain chiefs of Batende-majority villages were cited by many sources as having taken part in the planning of the attacks."
The U.N. investigators expressed concern that not enough had been done to prevent the violence and that the risk of conflict remains. "Provincial authorities appear to have failed in their responsibility to protect the population," the report said. "In spite of clear signs of rising tensions and an increased risk of violence, no steps were taken to reinforce security ahead of the attacks."
Congo's electoral commission barred voting in Yumbi because of the massacre, a controversial decision that also affected some 1 million people in eastern areas affected by an Ebola outbreak.
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