Since April 15, Sudan's regular army headed by Abdel Fattah al-Burhan has been locked in fighting with the RSF, commanded by his former deputy Mohamed Hamdan Daglo.

The fighting has sparked a humanitarian crisis, killing thousands and forcing millions of people to flee their homes, with the deadliest violence raging in the vast western region of Darfur that borders Chad.

The victims were killed in the West Darfur state capital El-Geneina between June 13-21 and the RSF ordered locals to bury them outside the city, said the UN's human rights office OHCHR.

Some of the victims belonged to the non-Arab Masalit ethnic group, while seven women and seven children were among the dead, the office said, adding that the RSF were "denying those killed a decent burial".

The UN had already received reports of Arab militia targeting Masalit men and said the conflict has taken on an "ethnic dimension".

OHCHR added that some people died from untreated injuries while others were victims of the violence that erupted following the killing of West Darfur's governor Khamis Abdullah Abakar in June.

UN rights chief Volker Turk said he was "appalled by the callous and disrespectful way the dead, along with their families and communities, were treated".

"There must be a prompt, thorough and independent investigation into the killings, and those responsible must be held to account."

He called on the warring parties to allow and facilitate searches for the dead.