Videos posted online and verified by Reuters show crowds gathering by the plane's burning wreckage. Reuters geolocated the site to northern Nyala, about 1 km from al-Mustaqbal neighborhood.

(Satellite images of the crash site from Planet)

Three aircraft experts said the downed plane was very likely an Ilyushin 76 cargo plane - similar to one downed in North Darfur in October - based on footage showing pieces of the engine and landing gear.

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An RSF source and a Western security analyst said the downing of an army plane on Sunday evening demonstrated new RSF anti-aircraft capabilities at Nyala. A local humanitarian source said the aircraft bombed the airport twice before it was shot down by anti-aircraft fire.

Sudan's army has repeatedly targeted Nyala and its airport, including with air strikes that have killed civilians, according to local activists and humanitarian workers in the area.

Analysis by the defence intelligence company Janes determined that the drones pictured are Chinese-manufactured CH-95s, capable of long-range surveillance and strikes at a distance of up to 200 km.

Satellite images show at least three drones and the construction of hangars at an airport in South Darfur held by Sudan's Rapid Support Forces (RSF), evidence of the continuing stream of increasingly advanced weapons fuelling a devastating war.

(Maxar images of the hangars Jan 14 and Feb 18)