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Residents gather to receive free meals in El Fasher, a city besieged by Sudan's paramilitary Rapid Support Forces for more than a year, in Darfur region, on Aug. 11.STR/AFP/Getty Images

Hundreds of thousands of besieged people in one of Sudan’s biggest cities, trapped by newly built walls and the threat of execution if they try to escape, are facing looming death from slow starvation or artillery shelling as the siege tightens.

El Fasher, capital of North Darfur region, has been surrounded by the paramilitary Rapid Support Forces for more than 500 days, with the RSF blocking humanitarian supplies as it seeks to capture the last major city in Darfur that it does not already control.

The city’s plight has become increasingly grim in recent days. The RSF has launched a fierce new offensive, killing dozens of civilians in shelling attacks, damaging hospitals, destroying food markets and water sources, and advancing closer to the Sudanese army base that defends the centre of the city.

Satellite photos, analyzed by Yale University’s Humanitarian Research Lab, show that the RSF has now built more than 31 kilometres of earthen walls around El Fasher, with construction of berms continuing over the past week, leaving most of the city encircled and exit routes controlled by the RSF.

Civilians who try to flee the city are routinely stopped by RSF fighters and are often subjected to looting, abductions and even summary execution, according to local media reports and Sudanese civil-society groups.

The newly constructed earthen berms will deepen the siege conditions. “The RSF is creating a literal kill box around El Fasher,” the Yale Humanitarian Research Lab said in a report on Friday.

“These berms will create physical boundaries to prevent smuggling goods like food and medicine into El Fasher or people out of El Fasher,” it said. “In the event of mass civilian exodus … RSF can easily kill civilians.”

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The killing resumed on the weekend. At least six civilians died and dozens were injured on Saturday as the RSF fired artillery shells into a market and other neighborhoods in the city, according to the Darfur Network for Human Rights and the Sudan Doctors Network.

Human-rights groups have voiced fears that an RSF takeover in El Fasher could trigger another ethnically targeted massacre against the non-Arab ethnic minorities in the city.

In 2023, RSF fighters killed an estimated 10,000 to 15,000 civilians when they captured the West Darfur city of El Geneina. The U.S. government has declared this year that the RSF and its allied Arab militias are committing genocide in Darfur, citing evidence that they have systematically killed and raped civilians on an ethnic basis.

The United Nations children’s agency, Unicef, estimates that 260,000 people are still inside El Fasher, including 130,000 children. They remain “trapped in desperate conditions, cut off from aid for more than 16 months,” the agency said last week.

More than 1,000 children in the city have already been killed or maimed in attacks over the past four months, Unicef said.

Hunger is an equally severe threat and “spreading fast,” the agency said. Malnutrition killed more than 60 people in El Fasher in a single week recently, while more than 10,000 children have been treated for severe acute malnutrition since January, nearly double the number in the same period last year, Unicef said.

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Just outside the city are sprawling refugee camps and informal shelters where more than a million people are struggling to survive in conditions that approach famine. Some have been forced to subsist on animal fodder and food waste, relief workers say.

The RSF blockade of humanitarian supplies has forced the suspension of health clinics and mobile nutrition teams that had helped children in the city, Unicef said. “Without therapeutic food and medical care, these children face an exponentially higher risk of death.”

Sudan’s war erupted in 2023 after a power struggle between the RSF and the Sudanese army. But it has allegedly been accelerated by weapons supplies from foreign countries, particularly the United Arab Emirates, a close ally of the RSF.

The UAE has denied supplying arms to the RSF. But aviation analysts have tracked a growing frequency of cargo flights from UAE to an air base in southeastern Libya. Social-media videos have shown convoys of trucks mobilizing in the desert of southeastern Libya to bring weapons across the border to RSF units in Darfur.

A number of civil-society groups, including U.S.-based Human Rights Watch, are urging the UN Security Council to impose sanctions on the RSF and to introduce a strict arms embargo on the entire country. The current UN arms embargo applies only to Darfur.

After losing control of Sudan’s capital, Khartoum, earlier this year, the RSF has sought to partition the country by creating a parallel government with its headquarters in Darfur. The RSF commander, General Mohamed Hamdan Dagalo, was sworn in as the head of the new parallel government on Saturday.

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