At least 13 people have been killed after an attack on one of the last remaining hospitals in el-Fasher, a Sudanese city trapped under siege.

Sixteen others, including a doctor and nurse, were injured after the paramilitary Rapid Support Forces (RSF) shelled Saudi hospital several times on Tuesday night, a source there told the BBC. A group of Sudanese medics has called the attack a war crime.

Pictures showed shattered windows, cracks from shrapnel, a gaping hole in the mud-brick wall and twisted metal from hospital beds covering the floor.

The RSF has been besieging el-Fasher for more than 17 months, leaving hundreds of thousands of people stuck in the city, facing starvation.

The paramilitary group is fighting the army for full control of el-Fasher, the last military stronghold in the vast Darfur region.

This is the second strike on the Saudi hospital this year - the first in January killed three children and injured three others. The latest shelling ripped through part of the hospital, destroying wards.

Experts warn that with intensified assaults on el-Fasher, the city could soon fall unless the army receives reinforcement.

Furthermore, recent research shows that the RSF has completed the construction of a wall around el-Fasher to bolster their siege, making it harder for civilians to escape. This wall has sealed all major exit routes and those attempting to leave face extortion, arbitrary detentions, and violence.

After over 500 days of nearly continuous violence, the UN has urged for immediate actions to protect civilians and alleviate the crisis in el-Fasher.