More than 70 people have been killed following a drone strike on a mosque in Sudan's Darfur region, a senior medical source has told the BBC.

Friday's attack in the city of el-Fasher has been blamed on the paramilitary Rapid Support Forces (RSF), but the group has not taken responsibility.

The RSF and the army have been engaged in a ferocious civil war for more than two years. The paramilitaries are gaining ground as they fight to seize complete control of el-Fasher - the last army stronghold in Darfur and home to more than 300,000 civilians who have been trapped by the fighting.

One resident told the BBC the drone struck during morning prayers, killing dozens of people instantly. The medical source specified that 78 died and about 20 were injured, but the process of extracting the bodies from the rubble of the building was still ongoing.

This week the RSF launched a renewed offensive on El Fasher, which it has besieged for more than a year. Reports say this included fierce attacks on Abu Shouk, a camp for displaced people near the city.

Satellite images suggest RSF units now control much of the camp, according to Yale University's Humanitarian Research Lab (HRL), which monitors wars. The HRL has indicated that without immediate reinforcements, el-Fasher will fall to the RSF, which would further solidify their control over the west of Sudan.

In light of ongoing hostilities, concerns are rising that the RSF might target civilians, particularly those from ethnic communities they oppose. The UN has reported on the escalating ethnic nature of the conflict, while condemning a systematic RSF policy of ethnic cleansing against non-Arab communities.

As the situation develops, the potential for increased violence against civilians in el-Fasher remains a grave concern.