The UN demanded an investigation Friday into reports of a second wave in months of ethnically-motivated killings in Sudan's Western Darfur region that have left hundreds dead.
The United Nations rights office said preliminary information it had obtained from survivors and witnesses suggested that Masalit civilians "suffered six days of terror" earlier this month.
"Some of the victims were summarily executed or burnt alive," spokesman Jeremy Laurence told reporters in Geneva.
The attacks began after the paramilitary Rapid Support Forces (RSF) and allied Arab militia took control of the Sudanese army's base in Ardamata, near West Darfur's capital, El Geneina, on November 4.
Focusing on two camps for internally displaced people in Ardamata and Dorti, and the majority Masalit Al-Kabri neighbourhood, the fighters "reportedly looted property, tortured IDPs, and executed many of them before leaving their bodies unburied in the streets", Laurence said.
"Many of those killed were young Masalit men and relatives of Sudanese soldiers," he said, adding that women and girls were reportedly subjected to sexual violence.
On November 5 alone, he said that "66 Masalit men were summarily executed in three separate incidents".
"Hundreds more men were arrested and taken to various RSF-run detention camps. Their fate and whereabouts remain unknown."
The attacks come amid a civil war that has been raging in Sudan since April 15, when forces loyal to army chief Abdel Fattah al-Burhan, Sudan's de facto head of state, went to war against the RSF, commanded by his former deputy Mahamed Hamdan Daglo.
More than 10,400 people have been killed in the Sudan conflict so far, according to one estimate by the Armed Conflict Location and Event Data project.
The war has displaced more than 4.8 million people within Sudan while a further 1.2 million have fled into neighbouring countries, according to UN figures.
Laurence pointed out that the Ardamata attack was the second reported mass killing of Masalit civilians by the RSF and its allies in a matter of months.
Between May and June, hundreds of Masalit men, women and children, including the governor of West Darfur, were killed, he recalled, stressing that "such attacks may constitute crimes under international law."
There have also been serious allegations of revenge attacks, in which Masalit militia have reportedly attacked Arab civilians.
Pointing to reports that an RSF assault is imminent on El Fasher, capital of North Darfur, Laurence stressed that all parties to the conflict are obliged under international law to "ensure protection of civilians and civilian infrastructure".
"All violations must stop immediately, and those responsible must be brought to justice following thorough, independent and impartial investigations," Laurence said.