The UN has called for safe passage for trapped civilians out of the Sudanese city of el-Fasher after paramilitary fighters announced they had seized control of the army's main base there.

Sudan's military has not acknowledged loss of the site, which would be a significant victory for the Rapid Support Forces (RSF) in the ongoing civil war. UN chief António Guterres said the latest fighting marked a terrible escalation in the conflict, adding that the suffering of civilians was unbearable, AFP news agency reports.

El-Fasher is the last army foothold in the vast western region of Darfur, and has been besieged by the RSF and its allies for 18 months. Heavy fighting has been reported since Saturday after RSF fighters captured the home of the North Darfur governor.

UN Human Rights chief Volker Türk warned that the risk of further large-scale, ethnically motivated violations and atrocities in el-Fasher is mounting by the day. The Sudanese Doctors' Network stated that the RSF had already carried out ethnically motivated killings and had looted medical facilities.

Communications to el-Fasher have been almost completely cut off, leaving those who managed to flee with harrowing tales of violence, with reports of massacres and ongoing conflict.

As the RSF claims to have seized control of the city, the UN's top humanitarian official Tom Fletcher emphasized their concerns for civilians trapped in the fighting, insisting they must be allowed safe passage and access to aid. The US is also pushing for safe passage and negotiating a ceasefire.

The RSF’s control of el-Fasher would mark a crucial comeback after previous setbacks, suggesting the civil war may continue unabated. Since the conflict began in 2023, over 150,000 people have lost their lives, and around 12 million more have fled their homes, exacerbating one of the worst humanitarian crises in recent history.