El-Fasher, Sudan - Thousands of civilians are feared trapped and in imminent danger in the Sudanese city of El-Fasher after its fall to paramilitaries, Doctors Without Borders said Saturday.

At war with the regular army since April 2023, the Rapid Support Forces seized El-Fasher on Sunday, pushing the military out of its last stronghold in Darfur after a grinding 18-month siege marked by starvation and bombardment.

Since the city's fall, reports have emerged of summary executions, sexual violence, attacks on aid workers, looting, and abductions, while communications remain largely cut off.

Survivors from El-Fasher who reached the nearby town of Tawila have told AFP of mass killings, children shot before their parents, and civilians beaten and robbed as they fled.

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The UN says more than 65,000 people have fled El-Fasher since Sunday, but tens of thousands remain trapped. Around 260,000 people were in the city before the RSF's final assault.

"Large numbers of people remain in grave danger and are being prevented by the Rapid Support Forces and its allies from reaching safer areas," Doctors Without Borders (MSF) said.

The NGO added that only 5,000 people had managed to make their way to Tawila, about 43 miles to the west.

The numbers of people arriving in Tawila "don't add up, while accounts of large-scale atrocities are mounting," said MSF head of emergencies Michel Olivier Lacharite.

"Where are all the missing people who have already survived months of famine and violence in El-Fasher?" he added.

"The most likely, albeit frightening, answer is that they are being killed, blocked, and hunted down when trying to flee."

Several eyewitnesses told MSF that a group of 500 civilians, along with soldiers from the military and the army-allied Joint Forces, had attempted to flee on Sunday, but most were killed or captured by the RSF and their allies.

Survivors reported that people were separated based on their gender, age, or presumed ethnicity, and that many were still being held for ransom.

Hayat, a mother of five who fled the city, previously told AFP that "young men traveling with us were stopped" along the way by paramilitaries and "we don't know what happened to them."

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The UN said Friday the death toll from the RSF's assault on the city may be in the hundreds, while army allies accused the paramilitary group of killing over 2,000 civilians.

Yale University's Humanitarian Research Lab suggested on Friday that mass killings were likely continuing in and around El-Fasher.

The lab, which uses satellite imagery and open-source information to document human rights abuses during wars, said fresh images from Friday showed "no large-scale movement" of civilians fleeing the city, giving them reason to believe much of the population may be "dead, captured, or in hiding."

The lab identified at least 31 clusters of objects consistent with human bodies between Sunday and Friday, across neighborhoods, university grounds, and military sites.

"Indicators that mass killing is continuing are clearly visible," the lab said.

At a conference in Bahrain on Saturday, German Foreign Minister Johann Wadephul said Sudan was "absolutely an apocalyptic situation, the greatest humanitarian crisis of the world."

He added that the RSF had "pledged to protect civilians and they will be held accountable for these actions."

Speaking at the same event, British Foreign Minister Yvette Cooper also described the reported abuses as "truly horrifying."

"Atrocities, mass executions, starvation and the devastating use of rape as a weapon of war, with women and children bearing the brunt of the largest humanitarian crisis in the 21st century," she said.

The RSF said Thursday that it had arrested several fighters accused of abuses during the capture of El-Fasher, but UN humanitarian chief Tom Fletcher questioned the group's commitment to investigating atrocities.

Both the RSF – descended from the Janjaweed militias accused of genocide in Darfur two decades ago – and the army have faced war crimes accusations over the course of the conflict.

The US has previously determined the RSF committed genocide in Darfur.

The RSF has received weapons and drones from the UAE, according to UN reports, though Abu Dhabi has denied giving any support to the paramilitary group.

Meanwhile, the army has drawn on support from Egypt, Saudi Arabia, Iran, and Turkey.

El-Fasher's capture gives the RSF full control over all five state capitals in Darfur, effectively splitting Sudan along an east-west axis, with the army controlling the north, east, and center.

UN officials have warned that the violence is now spreading to the neighboring Kordofan region, with reports emerging of "large-scale atrocities perpetrated" by the RSF.

The wider conflict has killed tens of thousands, displaced nearly 12 million, and created the world's largest displacement and hunger crises.