Humanitarian volunteers told Sky News around 70% of the city's half-a-million residents have fled since the start of the war in Sudan and that the bodies littering the streets are now buried at multiple mass grave sites after a huge clean-up operation.

The coordinates of potential mass grave sites on the outskirts of al Geneina shared by C4ADS, a Washington DC-based global security non-profit, have been verified by Sky News through various eyewitness accounts.

A satellite image from May shows regular mountainous terrain just north of the main artery connecting al Geneina to eastern Chad.

On 6 July, the same three areas are now visibly water-filled due to seasonal rainfall.

An eyewitness independently located this site for Sky News using landmarks on the map and says he watched as decomposing bodies were dumped into a body of water at the end of June.

"It was the start of the rainy season and they had disconnected the network so we had to go to the edges of the city to try and make calls," he said.

The pitch of his voice climbed with urgency as he described the scene.

"After the police station and over the mountain - around 250 metres from a cattle slaughterhouse - I saw a group of scared residents throwing nine bodies into a large pond."

'I lost 14 brothers and sisters'

One volunteer independently verified the location of this grave site and says he was present as 50 bodies were dumped there.

The next day, he was involved in the transportation of another 45 bodies.

"Our group was not happy with how the dead were being treated so we opted out of the burial. We helped with transporting the corpses but did not join for the dumping," he says.

He identified the victims as being from the African Massalit and Burgo tribes and says that volunteers could not film or even make a call around the site.

"One guy we know was suspected of leaking information and was beaten until his leg broke."

From the Burgo tribe himself, his own family has suffered from the extreme ethnic violence that ravaged al Geneina.

He says 14 of his brothers and sisters have been killed in al Geneina since the start of the war in April - many of them remained unburied for weeks after their deaths.

One of his sisters, a teenager, was shot in the head and killed in their home - a horrific incident corroborated by a humanitarian worker also in the city at the time.

"I buried my sister 54 days after she was killed. My mother was wounded at the same time and could not leave the house for a long time. She still hasn't received any medical assistance," said the volunteer, who is being kept anonymous for his safety.

He and his family are some of the remaining non-Arab residents in al Geneina.

His elderly father and wounded mother make leaving difficult and relocation funds are low after their savings were looted from their home amid the chaos.

The little income he gets from transporting bodies has helped him facilitate the burial of his family members.

'Assassination attempts' on volunteers trying to help

A humanitarian worker who has a long history of advocacy work in al Geneina believes that the city has been ethnically cleansed.

"The janjaweed militias practised forced displacement by burning homes and shelters for the displaced in a brutal and racist manner - killing civilians - which is considered a crime of genocide," he said.

He added the campaign to tidy up the city's emptied streets is led by Arab tribesmen and is an attempt to clean up the image of the Rapid Support Forces and their aligned militias who have been caught filling up mass graves.

"The Rapid Support Forces, along with Arab militias, participated by providing digging mechanisms such as bulldozers and trucks - in addition to designating burial areas. Sometimes they even participated with volunteers," the source says.

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Another mass grave site is reported on the northern outskirts of the city, along Tendelti road - a border town which was razed to the ground in May.

And even in this moment of relative calm in al Geneina, those told to bury the evidence of violence are facing violence themselves.

"There have been some assassination attempts in al Geneina these days of some of the volunteers who participated in the preparation and burial of bodies in the mass graves," he says.

"The latest of which is the attempted assassination of the manager of the Sudanese Red Crescent in West Darfur, who was shot with live bullets and is now under medical care in Chad."