The Sudanese army on Monday withdrew fromEl-Fasher, its last stronghold in the Darfur region as the city was seized by the Rapid Support Forces (RSF) paramilitary groupfollowing an 18-month siege that left citizens on the brink of famine.The fall of El-Fasher could herald another split of Sudan, more than a decade after South Sudans creation.

Sudan army chief General Abdel Fattah al-Burhan said on Monday that "the army has withdrawn from El-Fasher", following an announcement that the city was seized by the Rapid Support Forces (RSF) paramilitary group.

"We have agreed to withdraw the army from El-Fasher to a safer location," Sudan's de facto ruler said in a speech broadcast on national television, asserting that his side "will take revenge" and fight "until this land is purified".

The statement was the first by al-Burhan acknowledging the loss in El-Fasher after the RSF, whose army troops have been fighting since April 2023, announced their victory in the city in western Darfur on Sunday.

Medical groups earlier reported dozens of civilians killed in the violence.

The army's withdrawal from the city of El-Fasher left over a quarter-million people half of them children under the control of the RSF, and aid groups reported chaotic scenes Monday, including battles between RSF and departing troops and their remaining allies. The UN accused the RSF of executing civilians.

The fall of El-Fasher to the RSF could herald another split of Sudan, more than a decade after South Sudans creation. The latest war started in April 2023 when tension between the military and RSF exploded into fighting in the capital, Khartoum, and elsewhere in the northeastern African country.

Footage posted on social media since Sunday shows RSF fighters celebrating in and around the former army base in El-Fasher. According to one video, the paramilitarys deputy commander, Abdulrahim Dagalo, called on his fighters not to loot or target civilians.

Other footage shows RSF fighters shooting and beating people as they attempt to flee. Many were shown detained. RSF fighters were heard shouting falangayat at detainees a racist term used to refer to African tribes in Darfur as slaves. Outraged Sudanese took to social media to denounce the attacks.

Read moreSudan's paramilitary Rapid Support Forces claim capture of key Darfur city

Military officials confirmed that troops had vacated the base on Sunday and retreated to another line of defence under heavy RSF shelling and artillery. By late Monday, al-Burhan said military officers decided to withdraw from the city entirely in hopes of sparing the civilian population from further violence.

The army retreated because of the systemic destruction, and the systemic killing of civilians by the RSF, he said in a televised speech, adding that the army hoped to spare the citizens and the rest of the city from destruction.

Resistance Committees in El-Fasher, a grassroots group tracking the war, reported earlier Monday that fighting was raging around the army base's airfield, as well as on the western side of the city. The group said the Sudanese troops had no visible air support in El-Fasher to try and fend off RSF attacks.

The UN Human Rights Office said in a statement that RSF fighters reportedly carried out atrocities in El-Fasher, including summary executions" of civilians trying to flee their attacks, with indications of ethnic motivations for killings".

Volker Turk, the UN high commissioner forhuman rights, said the risk of further large-scale, ethnically motivated violations and atrocities in El-Fasher is mounting by the day.

Read moreRSF paramilitary drone strike kills at least 75 people in war-torn Sudan

Satellite images analysed by The Associated Press showed the headquarters of the militarys 6th Division, with the roofs of multiple buildings damaged. The layout of the headquarters corresponded to details seen in footage released by the RSF, showing their fighters gathering around one bullet-scarred building, heralding their capture of the city.

Yale University's Humanitarian Research Lab also confirmed through satellite imagery that the paramilitaries advanced as far as the 6th Division headquarters, with significant evidence of close-quarter battle in the area. The lab said in a statement Sunday that it identified activities likely showing RSF taking prisoners in and around the airfield.

The Sudan Doctor Network, a medical group tracking the war, described the RSF attack as a heinous massacre and said dozens of people were killed.

RSF fighters rampaged through parts of El-Fasher, looting hospitals and other medical facilities and destroying what remained of essential life-supporting and health care infrastructure", the network said in a statement.

The Darfur Network for Human Rights said the RSF detained over 1,000 civilians, describing it as systematic targeting of civilians, arbitrary detentions and potential acts amounting to war crimes.

Among the detained was a local journalist, one of the few left in the city, according to the Sudanese Journalists' Union. The group warned about potential mass violations in El-Fasher, similar to what happened in another Darfur city, Geneina, in 2023 when RSF fighters killed hundreds.

The Doctors Union, the professional umbrella of Sudanese physicians, said RSF turned El-Fasher into a brutal killing field, calling its practices in Sudan a barbaric policy that aims at terrorizing and annihilating civilians. The group urged the international community to classify the RSF as a terrorist organisation.

UN humanitarian chief Tom Fletcher expressed deep alarm at reports of civilian casualties and forced displacement in El-Fasher.

Hundreds of thousands of civilians are trapped and terrified shelled, starving and without access to food, health care or safety, he said in a statement. He called for safe, rapid and unimpeded humanitarian access to the population that remained.

Before Sundays attack, there were 260,000 civilians, half of them children, trapped in El-Fasher, according to the UN childrens agency.

Read moreSudan war's devastating impact on women and girls

The UN's International Organization for Migration said more than 26,000 people had fled their homes as of Monday, retreating to rural areas and to the overwhelmed nearby town of Tawila.

Elsewhere, RSF fighters ran riot in the town of Bara in the central Kordofan region over the weekend, killing at least 47 people, including nine women, the Sudan Doctor Network said.

The RSF grew out of the notorious Janjaweed Arab militias that brutalised the Sudanese during the Darfur conflict in the 2000s.

The latest war has killed over 40,000 people and created the worlds worst humanitarian crisis, with part of the country, including the El-Fasher area, plunged into famine. Over 14 million people have fled their homes.

The conflict has been marked by gross atrocities, including ethnically motivated killings and rape, according to the UN and rights groups.

The International Criminal Court has said it was investigating alleged war crimes andcrimes against humanity.

Originally published on France24