- At least 87 people were found in a Sudan mass grave.
- The UN believes the Rapid Support Forces were responsible.
- Egypt is hosting talks between the warring Sudan factions.
At least 87 people including ethnic Masalits were buried in a mass grave in Sudan's West Darfur, the UN human rights office said on Thursday, saying it had credible information that the Rapid Support Forces were responsible.
"I condemn in the strongest terms the killing of civilians and hors de combat individuals, and I am further appalled by the callous and disrespectful way the dead, along with their families and communities, were treated," said UN High Commissioner for Human Rights Volker Turk in a statement.
He called for a prompt and thorough investigation.
In the meantime, Egypt is attempting to mediate between Sudan's warring factions, hosting a regional summit on Thursday, the latest in a series of international efforts to prevent the outbreak of civil war and the deepening of a humanitarian crisis.
Fighting between Sudan's army and paramilitary Rapid Support Forces broke out in the capital Khartoum in April and has spread westward to the fragile Darfur and Kordofan regions.
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More than 1 000 civilians have been killed and three million people have been displaced, according to the UN, which warns of a growing hunger crisis.
The United States and Saudi Arabia had negotiated a series of ceasefires, but suspended talks after violations.
Earlier this week, Ethiopia hosted a regional East African summit, but the army boycotted, claiming Kenya, the lead sponsor, was biased.
Egypt, which has historically close ties with the Sudanese army, invited Sudan's neighbours to the Thursday summit.
The aims of the summit are to stave off foreign interference and influence in the fighting, two Egyptian security sources said, and to ultimately launch a process to achieve a peaceful agreement to stop the fighting.
That plan aims to achieve a three-month ceasefire and open aid pathways amid a series of meetings with military and tribal leaders, the sources said.
Previous one-day and multi-day ceasefires were quickly violated and were described by the UN special envoy Volker Perthes as an opportunity for the forces to re-position.
Speaking on Wednesday, he described mediation attempts as "emergency diplomacy".
He said:
Among the African leaders attending is Ethiopian prime minister Abiy Ahmed, whose country has clashed with Egypt over its construction of a giant dam on the Blue Nile.
He met Egypt's President Abdel Fattah al-Sisi on Wednesday, after last week saying the fourth filling of the dam this summer would be delayed and would ensure Sudan and Egypt would receive enough water, a conciliatory move after years of tension.