Attacks around the Sudanese city of al-Fashir have shattered a truce that protected it from a year-old war, leading to warnings of a new wave of inter-communal violence and humanitarian risks for 1.6 million residents crammed into the North Darfur capital.
Al-Fashir is the last major city in the vast, western Darfur region not under paramilitary Rapid Support Forces (RSF) control.
The RSF and its allies swept through four other Darfur state capitals in 2023 and were blamed for a campaign of ethnically driven killings against non-Arab groups and other abuses in West Darfur.
The fight for al-Fashir, a historic centre of power, could be more protracted, inflame ethnic tensions that surfaced in the early-2000s conflict in the region and reach across Sudan's border with Chad, residents, aid agencies and analysts say.
Al-Fashir's population includes an estimated half a million people displaced during that earlier conflict, when the army, assisted by Arab militias that evolved into the RSF, put down a rebellion by non-Arab rebel groups.
About half a million more people moved into the city when war broke out between the army and the RSF in the capital Khartoum in April 2023, as long-simmering tensions over integrating the two forces came to a head.
As the war spread to other parts of the country, local leaders brokered a truce in al-Fashir, with the RSF confined to eastern areas of the city while the former rebel groups stayed neutral.
But the arrangement fell apart after the RSF took the town of Melit this month, effectively blockading al-Fashir.
Witnesses say the army has reinforced supplies and troops, including through an airdrop to its base in the city, unlike in other state capitals where soldiers quickly fled.
Two prominent former rebel groups, Minni Minawi's Sudan Liberation Army (SLA) and Jibril Ibrahim's Justice and Equality Movement, said they would defend against the RSF.
Even before the truce collapsed, occasional skirmishes killed more than 220 people in al-Fashir in the past year, according to Ismail Khareef, an activist in Abu Shouk, one of the displacement camps that dot the city.
Khareef said at least 18 people died in clashes on April 16.
Gunfire and projectiles, including from army warplanes, have fallen on homes, he and other residents said.
At least 11 villages on al-Fashir's outskirts have been razed since April 1, satellite imagery obtained by the Yale Humanitarian Research Lab shows.
At least 36,000 have been displaced, the United Nations estimates.
Local activists and an SLA spokesperson blamed the RSF and allied militias, who have been known to use arson in past attacks, including in West Darfur.
The activists said survivors of the attacks reported about 10 people killed and said the attackers used ethnic insults.
The RSF denied attacking al-Fashir and said it was careful to keep clashes away from civilians, accusing the army and allied groups of attacking it on the outskirts.
The RSF has previously denied responsibility for ethnic violence in Darfur.
The army did not immediately respond to requests for comment.
Al-Fashir itself has not had functioning running water or power lines for a year, Darfur director for Practical Action Awadalla Hamid said.
Speaking to Reuters from the city, where few international humanitarians remain, he said only one public hospital was functioning, while displaced people were crammed into schools and public buildings.
Jerome Tubiana, an expert on Darfur and advisor to medical charity MSF, said all-out fighting "risks already complicating further humanitarian access, at a time where available data shows al-Fashir is suffering of an extremely serious food crisis".
Recent tensions and violence around al-Fashir have also raised concerns about a wider spillover.
The former rebel groups fighting alongside the army hail from the Zaghawa tribe, which reaches across the border into Chad, counting Chadian leader Mahamat Idriss Deby as a member.
