Hunger and disease has spread across the city as residents contend with constant bombardment and dwindling food and medical supplies.
UN investigators have accused the RSF of committing numerous crimes against humanity during the siege. The US has said the RSF has committed genocide against Darfur's non-Arab population.
Sudan has been ravished by conflict since 2023, after top commanders of the RSF and Sudanese army fell out and a vicious power struggle ensued.
More than 150,000 people have died across the country and about 12 million have fled their homes, creating one of the worst humanitarian crises.
The army controls most of the north and the east, with el-Fasher being until now the last major urban centre in Darfur still held by government forces and its allies.
The RSF controls almost all of Darfur and much of the neighbouring Kordofan region.
When the RSF assumes complete control of el-Fasher, it hopes to form a rival government there.
Additional reporting by Peter Mwai
