GENEVA (Reuters) - A militia group blamed for atrocities in Congo is largely composed of children, while a militia formed to defeat it is suspected of a campaign of ethnically based massacres and rapes, U.N. investigators said on Friday.
The report, detailing violence that the United Nations said may amount to crimes against humanity, shines a light onto the role of children and witchcraft in a conflict that has killed thousands.
It was based on testimonies from refugees who had fled from the violence in Democratic Republic of Congo to Angola.
"Their accounts should serve as a grave warning to the government of the DRC to act now to prevent such violence from tipping into wider ethnic cleansing." U.N. High Commissioner for Human Rights Zeid Ra'ad al-Hussein said in a statement.
The investigation, which was "triggered because the response of government fell short", documented 251 killings over a three-month period in an area that covers only a fraction of the 59,000 square mile (152,800 sq km) diamond-rich Kasai region.
Responding to the report, a spokesman for the Congo government said it would investigate and punish crimes.
The report said that one militia group, the Kamuina Nsapu, has been fighting Congo's government for a year, and has summarily executed at least 79 people.
"A great majority of the Kamuina Nsapu elements are children (girls and boys), some as young as seven," it said.
The refugees were convinced that the Kamuina Nsapu had magical powers, and militia members believed their magic -- including young girls drinking the blood of decapitated victims -- would make them invincible, the report said.
"This generalized belief about the powers of Kamuina Nsapu and the fear it triggers among segments of the population in the Kasais may partly explain why a poorly-armed militia, composed to a large extent of children, has been able to resist offensives by a trained national army for over a year."
There were no corroborated cases of Kamuina Nsapu committing large-scale killings based on ethnic identity, the report said. Typically its members would execute a government official and decapitate them, removing the head to put it in "sacred fire".
A second militia group, the Bana Mura, was formed in March or April, allegedly armed and supported by local leaders and officials from the army and the police, to attack the Luba and Lulua ethnic groups, to which Kamuina Nsapu fighters belong.
"The Bana Mura allegedly undertook a campaign aimed at eliminating the entire Luba and Lulua populations in the villages they attacked," the report said.
Scott Campbell, head of Central and West Africa at the U.N. human rights office, said the violence had spiraled out of control with the complicity of the government of President Joseph Kabila, whose mandate expired last December, and the U.N. was concerned it could be used to delay a fresh election.
The Congo government says the convictions of seven soldiers last month for murdering suspected militia members in Kasai show the justice system is acting.
Government spokesman Lambert Mende told Reuters on Friday: "If it is the Bana Mura that have killed Congolese people, we will arrest them and bring them to justice."
He did not confirm or deny any elements of the U.N. report but said that it would help Congo with an upcoming investigation in Kasai, to be led by three human rights experts appointed by the United Nations.
The U.N. report said the Bana Mura were often accompanied by Congolese soldiers, who were responsible for atrocities including firing rockets into a church in the village of Djiboko on 10 June, killing 60-90 people attending a religious service.
In one attack on a village, the Bana Mura shot, chopped up and disemboweled people. Many were beheaded or burned alive, including the patients in a health center, the report said.
A woman still bleeding from childbirth was raped with the barrel of a rifle, it said. After a Bana Mura attack on another village, one witness claimed to have buried 45 decapitated bodies.
Reporting by Tom Miles; Additional reporting by Amedee Mwarabu in Kinshasa; Editing by Catherine Evans and Alister Doyle