El-Fasher is the last major location in North Darfur under army control. Civilians and military personnel there have been under attack by the RSF for over a year.
Four members of the UN convoy travelling to el-Fasher were killed on Monday night and two more were injured, RSF spokesperson Basha Tabiq said in a post on X.
The el-Koma Emergency Room, a group of local volunteer responders, posted a video of a burnt out truck, loaded with sacks of supplies, on Facebook. They blamed the attack on "Sudanese army drones".
El-Koma, which is controlled by the RSF, has previously been the target of frequent attacks in the conflict between the paramilitary group and the army.
Assaults on the city have resulted in civilian deaths and damaged key infrastructure.
The el-Koma Emergency Room said at least 89 people were killed or injured after Sudanese army warplanes launched airstrikes in the town on Sunday. The army has not responded to this accusation.
According to the Sudan Tribune news website, the planes struck a busy market in el-Koma.
The war, which began more than two years ago, has created one of the world's worst humanitarian crises.
On Tuesday Eujin Byun, a spokesperson for the UN refugee agency, said more than four million people have fled since the beginning of the conflict.
The civil war broke out in 2023 following a vicious struggle for power between the army and the RSF.
The two had jointly staged a coup to derail Sudan's transition to democracy, before their commanders fell out.
