The resistance committee for El-Fasher, the North Darfur state capital, said the RSF hit the Dar al-Arqam displacement centre on the grounds of a university.
"Children, women and the elderly were killed in cold blood, and many were completely burned," it said.
"The situation has gone beyond disaster and genocide inside the city, and the world remains silent."
The committee had initially put the toll at 30 dead, but said bodies remained trapped underground.
It later said 60 were killed in the attack involving two drones and eight artillery shells.
The local resistance committees are activists who coordinate aid and document atrocities in the Sudan conflict.
The RSF has been at war with the regular army since April 2023. The conflict has killed tens of thousands of people, displaced mi