The leader of Sudan's paramilitary Rapid Support Forces (RSF) has declared an investigation into what he called violations committed by his soldiers during the capture of el-Fasher.

The announcement by Gen Mohamed Hamdan Dagalo, known as Hemedti, came after escalating reports of mass civilian killings following the RSF takeover of the city in the Darfur region on Sunday.

The UN Security Council is expected to hold a meeting on Sudan, which is in its third year of civil war between the army and the paramilitary fighters.

The RSF leader spoke after international outrage about reports of mass killings in el-Fasher, apparently documented by his paramilitary fighters in social media videos.

Hemedti said he was sorry for the disaster that had befallen the people of el-Fasher and admitted there had been violations by his forces, which would be investigated by a committee that has now arrived in the city.

However, observers have noted that similar promises made in the past - in response to accusations of a massacre in the Darfuri city of el-Geneina in 2023, and alleged atrocities during the group's control of the central state of Gezira - were never fulfilled.

The UN World Health Organization (WHO) has said it is appalled and deeply shocked by reports that more than 460 civilians, including patients and their companions, were shot dead, at the last partially functioning hospital in el-Fasher.

The RSF denies widespread allegations that the killings in el-Fasher are ethnically motivated and follow a pattern of the Arab paramilitaries targeting non-Arab populations.

Activists have also stepped-up demands for international pressure on the United Arab Emirates (UAE), which is widely accused of providing military support to the RSF.

The UAE denies this despite evidence presented in UN reports.

El-Fasher had been the army's last stronghold in the western region of Darfur, and was captured by the RSF after an 18-month siege marked by starvation and heavy bombardment.

The takeover of el-Fasher reinforces the geographic split in the country, with the RSF now in control of western Sudan and much of neighbouring Kordofan to the south, and the army holding the capital, Khartoum, central and eastern regions along the Red Sea.

The two warring rivals had been allies - coming to power together in a coup in 2021 - but fell out over an internationally backed plan to move towards civilian rule.