Warning: This story contains graphic descriptions of executions.

Fighters from the paramilitary Rapid Support Forces (RSF) have executed a number of unarmed people after capturing the Sudanese city of el-Fasher, new videos analysed by BBC Verify show.

The RSF, which has engaged in a brutal war with the Sudanese Armed Forces (SAF) for more than two years, seized a key military base in the city over the weekend after an extended siege.

Several videos have since emerged showing men wearing military fatigues with some wearing what appear to be RSF patches carrying out extreme acts of violence around el-Fasher. The UN’s Sudan coordinator said it had received “credible reports of summary executions” in the city during an interview with the BBC on Wednesday.

BBC Verify has approached the RSF for comment. Imran Abdullah, an adviser to the RSF, denied the group’s fighters were targeting civilians in an interview with the BBC on Monday.

Sudan has been ravaged by war since the conflict broke out in 2023, prompted by the collapse of the SAF and the RSF’s fragile ruling coalition. More than 150,000 people have died across the country and about 12 million have fled their homes since then.

Speaking to BBC Radio 4’s Today programme, Denise Brown – the UN’s Sudan coordinator – said she had received reports of executions against “unarmed men in particular” since the RSF entered the city. Killings of unarmed civilians or surrendering combatants is a war crime under the Geneva Convention.

Most of the clips reviewed by BBC Verify are in dusty and sandy rural locations, making it hard to say where exactly they took place. However, we did geolocate one video showing the summary shooting of an unarmed man at a university building in el-Fasher.

The clip showed the unarmed man sitting amid dozens of dead bodies in a hallway. As the video progressed, he was seen turning towards the camera which followed an armed man who was descending the stairs. The fighter then raised his rifle and fired a single shot knocking the unarmed man to the ground, where he lay motionless.

A number of similarly distressing clips are circulating online, but are difficult to geolocate as they are recorded outside the city itself where there are very few visible landmarks. But BBC Verify has managed to place one of the fighters who appeared in multiple execution videos in the area around el-Fasher in recent days.

The fighter, who goes by the name of Abu Lulu, has long had his activities with the RSF documented on a social media profile viewed by BBC Verify.

A video which first appeared online over the weekend showed him amidst dead bodies in an area north-west of the city. Working with the Centre for Information Resilience (CIR), BBC Verify has been able to confirm the location of this footage, but it’s difficult to say whether the dead in the clip are civilians or SAF troops killed in fighting due to the quality of the video.

But Abu Lulu has also appeared in at least two videos which show him participating in the execution of unarmed men who are kneeling and under armed guard. Reverse image searches show all the videos have appeared online since the weekend.

In one video he was seen addressing an injured man lying on the ground, berating him for not sharing information before threatening to rape him. The RSF fighter then shot the captive several times using an automatic rifle.

A separate video shows Abu Lulu standing alongside several RSF troops carrying AK-style assault rifles and guarding a group of at least nine unarmed captives. After addressing the men, Abu Lulu aimed his rifle at the group and opened fire. In the aftermath the other armed men raised their arms and cheered.

In another clip the fighter was seen standing alongside several other armed men with dozens of dead bodies visible in the background. Some of the fighters were wearing RSF style uniforms, one of which has a circular patch with a black line running around the circumference – consistent with the paramilitary’s insignia.

In August the RSF said it would investigate Abu Lulu after he was accused of executing a captive. A statement said “if it is proven that the perpetrator is indeed a member of our ranks, he will be held accountable without delay”.

The videos come after US-based researchers said that satellite images taken of el-Fasher since the city fell appear to show the aftermath of mass killings carried out in the streets of the city itself.

Analysts with the Yale Humanitarian Research Lab highlighted large “clusters” visible in the images, which they said were “consistent with the size range of adult human bodies and are not present in previous imagery”.

In the report issued on Monday, Yale said that its analysts’ observations were “consistent with reports of executions” shared online and by the UN and human rights groups in recent days and also highlighted “discoloration” which the analysts said may be human blood.

Without on-the-ground footage from that location, BBC Verify cannot independently confirm Yale’s findings.

Other satellite images viewed by BBC Verify appeared to show vehicles parked at each end of several streets. Yale analysts noted that their positioning appeared to suggest that the paramilitary was carrying out house-to-house clearance operations. In some areas, clusters that Yale identified as human bodies were seen near the vehicles.

Michael Jones, an analyst with the Royal United Services Institute (RUSI), said the RSF has a track record of carrying out ethnically-based summary killings which could be partially attributed to the paramilitary’s “decentralised composition”.

“The bulk of the group’s manpower comes from a messy confederation of rented militia, local allies and economic opportunists, who are often motivated by interests or grievances that pre-date the April 2023 conflict,” he told BBC Verify.

“Although likely playing out under the umbrella of RSF policy, the violence can sometimes be decentralised, with perpetrators settling personal or communal vendettas, seizing assets or land, and participating in ethnic cleansing to consolidate their own political power.”

In recent months the SAF has made several major gains against the RSF, including recapturing the capital Khartoum, so that the army now controls most of the north and the east of the country.

By contrast the RSF controls almost all of Darfur in the west and much of the neighbouring Kordofan region – the traditional base of its predecessor, the Janjaweed paramilitary which carried out ethnic killings in Darfur between 2003 and 2005. Many of those who fought with the Janjaweed are believed to have joined the RSF.

Until now el-Fasher was the last major urban centre in Darfur still held by government forces and its allies. The RSF has previously said that it hopes to form a rival government in the city when it had assumed control there.

Both sides have been accused of war crimes since the conflict began and in the closing days of President Joe Biden’s administration the US said the RSF had carried out acts of genocide. BBC Verify has previously documented mass killings carried out by the RSF following the defection of a senior commander.

Additional reporting by Kumar Malhotra, Benedict Garman, Richard Irvine-Brown, Daniele Palumbo, Paul Myers and Thomas Copeland.