Russia's embassy in Sudan has said it is investigating reports that a cargo plane with Russian crew was shot down in Darfur, a key battle ground in the civil war between the army and the paramilitary Rapid Support Forces (RSF).

The aircraft, identified as a Russian-made lyushin Il-76, was on a mission to deliver equipment and medicine to the army-held city of el-Fasher, military sources told Sudanese media.

On Monday, the RSF said it had downed a Russian-made plane flown by the Egyptian military that it accused of bombing civilians - though it was identified as an Antonov.

Egypt denies accusations that it has been providing military support to Sudan's army during the 18-month conflict.

The vicious struggle for power between the army and RSF began in April 2023, leading to what the UN has called one of the world's worst humanitarian crises.

Some estimates suggest up to 150,000 people have been killed since the war began last year, according to comments made in May by US special envoy for Sudan Tom Perriello.

The UN estimates it has also forced more than 10 million people - about a fifth of the population - from their homes.

Details about the crash and its mission are murky.

The Russian embassy in the capital, Khartoum, said it was co-ordinating with the Sudanese military-led government to gather more information about the crash and those who were onboard.

According to the Sudan Tribune news website, all members of the crew - including three Sudan nationals and two Russians - were killed in the crash.

It quotes military sources as saying it came down in the Malha area, near the border with Chad, en route to the besieged city of el-Fasher. This has not been independently verified.

El-Fasher is the only city still under army control in the western Darfur region - and has been under attack from the RSF since April.

The RSF says it has the plane’s black box and seized documents related to the plane and its mission.

Viral footage from the alleged scene of the crash shows RSF soldiers with what appears to be identification documents next to the plane wreckage.

According to BBC Verify, the documents - including a Russian passport, a job identification card from Manas airport in Kyrgyzstan and two South African driving licences (with different expiry dates) - all relate to one individual.

Preliminary research suggests he may have graduated from a Russian military academy and may have been a resident in South Africa.

One video posted by the RSF also shows a fighter holding up 50-rouble ($0.50; £0.40) Russian currency note - however the way it is filmed makes it hard to tell conclusively that the footage was shot near the crash site.

Some reports suggest a technical fault may have been responsible for the crash - but both the army and RSF are saying it was shot down.

Others indicate it may have mistakenly been targeted.

This is because some documents seen in circulating video footage suggest the aircraft was affiliated with an airline previously linked to the United Arab Emirates (UAE).

The Middle Eastern country denies allegations that it has been arming the RSF - though the UN says there is credible evidence.

Fresh diplomatic attempts to negotiate a cessation of hostilities between the rival forces in Sudan have failed to make progress.

Fierce fighting has recently escalated around Khartoum, which is largely controlled by the RSF, with the military intensifying airstrikes in the city's centre and southern belt.

In Wad Madani, an RSF-held city south of Khartoum in Gezira state, local activists say more than 50 people have been killed in multiple attacks since Sunday.

The city’s “resistance committee”, made up of volunteers who try to bring aid locally to those caught up in the conflict, says more than 30 people were killed on Sunday in a military airstrike on a mosque.

It says the attack happened after evening prayers and accuses the army of using barrel bombs - banned from use in populated civilian areas under international conventions - and rescuers have been unable to identify over half of the dead as the bodies are charred and mutilated.

The attacks follow the recent defection to the army of the RSF’s top commander in Gezira state.

Additional reporting from BBC Verify’s Peter Mwai.