In the video, he identifies hismelf as Andrew Hill and was part of the foreign legion in Ukraine.
Asked by his questioners about his rank, the said: "I don't have a rank. I just know the foreign legion said I could help."
During the video, he is seen with a heavily bandaged left arm and a bandage around his head.
He then says that his father passed away on New Year’s Eve and that he does not have a relationship with his mother.
Mr Hill adds that he has four children and a partner. He says that his passport had been taken by Russian soldiers.
Mr Hill is now the third person to have been detained by Russian troops in Ukraine.
This comes after it emerged that fellow UK national, Scott Sibley, 36, had been killed fighting in Ukraine.
The Foreign, Development and Commonwealth Office confirmed a second man is also missing, adding in a statement: “We are aware of a British National who is missing in Ukraine and are supporting their family. We are urgently seeking further information.”
British nationals, Aiden Aslin, 28, and Shaun Pinner, 48, were also captured earlier this month by Russian forces.
Presidium Network, a non-profit organisation, said the two workers were detained at a checkpoint south of the city of Zaporizhzhia.
The Foreign Office is urgently seeking more information on the claims.
“The Foreign Office is doing all it can to support and identify these two people,” Anne-Marie Trevelyan, the international trade secretary, told Sky News.