John Harding, in his fifties and from Sunderland, says he was told he could face the death penalty.
A British man has been shown in a video appealing for help from Boris Johnson, while appearing to be held captive by pro-Russian separatists in the self-proclaimed Donetsk People’s Republic (DPR) in eastern Ukraine.
John Harding, who is in his fifties and originally from Sunderland, is being interviewed by a Russian TV presenter.
In the video he calls for help from the UK prime minister.
He says he has been told he could face the death penalty.
It is understood John Harding was captured in May while fighting with the Azov regiment, part of the Ukrainian National Guard, when Ukrainian units who had been defending the south-eastern city of Mariupol were forced to surrender.
Friends and family of John Harding confirmed to the BBC it was him in the video, and his family are being supported by the Foreign Office.
John Harding had been fighting in eastern Ukraine’s Donbas region since 2018. He previously told the BBC he had travelled there to use his skills as a combat medic, to help in the fight against pro-Russian rebels.
Two other British men, Aiden Aslin and Shaun Pinner, who were also captured in Mariupol, have been sentenced to death by a Russian proxy court in the DPR.
Both they and John Harding had moved to Ukraine around the same time and made the country their home.
The DPR court is not internationally recognised. Foreign Secretary Liz Truss has has called the death sentences a “sham judgement with absolutely no legitimacy”.
The UK government has said they should be treated as prisoners of war under the laws laid out in the Geneva Conventions.
This week Paul Urey, a British aid worker, died while being held by pro-Russian separatists in east Ukraine. Officials from the DPR said he died in captivity on 10 July from underlying health conditions and “stress”.
The Foreign Office has been contacted for comment on the Harding case.