berm

Satellite images show that troops started to construct a massive berm - a raised sand barrier - around the perimeter of el-Fasher, sealing off access routes and blocking aid.

They constructed a 35-mile earthen berm around the city in an attempt to encircle its one million residents.

Between the outpost and the ruins rises a sand berm about two stories high and topped with barbed wire.

Earlier this year, the militia tightened its hold on El Fasher by walling it off with a sand berm, according to satellite photos published in August by the Yale Humanitarian Research Lab.

BBC Verify says both sides in the conflict have been using berms as a defensive strategy.