Warning: This story contains descriptions of torture and physical violence. Some readers may find it distressing.

A shopkeeper has told the BBC how Russian mercenaries fighting jihadists in Mali carried out the cold-blooded murder of two men in front of him and then threatened to chop off his fingers and kill him too.

This is one of several similar testimonies collected by the BBC showing the tactics used by the Russian fighters as they waged a brutal counter-insurgency operation against Islamist militants in the West African nation - methods widely condemned by human rights groups.

A military junta seized power in Mali in 2021, forcing French troops to leave after accusing them of failing to stem the insurgency. The junta pivoted towards Russia, enlisting the help of the Wagner mercenary group, which was at the time linked to the Kremlin.

Wagner has since pulled out of the country, and its operations have been taken over by Africa Corps, which falls under Russia's defence ministry. Some Wagner mercenaries highlighted their atrocities on an invitation-only Telegram group until it was shut down in the middle of this year, according to a report released by the European Council on Foreign Relations.

In June, the Africa Report publication said it had infiltrated the Wagner-linked Telegram channel, finding 322 videos and 647 photographs of atrocities, including severed heads and gouged-out eyes, and posts laced with racism.

The shopkeeper we spoke to has fled Mali and is now living in a refugee camp across the border in Mauritania. We have named him Ahmed, and have changed the names of all the victims quoted in this article for their own safety.

During his ordeal in August 2024, Ahmed was taken by Wagner fighters who accused him of colluding with jihadists. Following severe torture involving waterboarding, he witnessed executions, threatening further violence if he did not disclose information about his boss.

Ahmed's experience is representative of the widespread abuses happening in the region, leading many to flee to neighboring countries like Mauritania. These atrocities have created a profound sense of fear and trauma among survivors and refugees alike.

A UN report states that nearly 50,000 people have fled to refugee camps in Mauritania, underscoring the gravity of the situation in Mali. The conflict, coupled with the presence of mercenaries, continues to breed instability in the region.

Despite the withdrawal of Wagner, the subsequent operations by Africa Corps remain a source of concern for human rights advocates, with reports suggesting a continuity of violence against civilians.

Ahmed, reflecting on the harrowing experiences, calls for justice, yearning for accountability for the atrocities committed by the mercenaries. The chilling reality faced by him and countless others echoes deeply in the humanitarian crisis unfolding in Mali.