Russian television late Thursday broadcast images of a young man handcuffed and with a cut on his forehead, saying his name was Aiden Aslin.

Aslin's mother, Ang Wood, told the British newspaper she knew it was her 28-year-old son because of his distinctive tattoo.

"Aiden is a serving member of the Ukrainian armed forces, and as such is a prisoner of war and must be treated with humanity," she was quoted as saying by the newspaper.

She holds Russian President Vladimir Putin "to the terms of the Geneva Convention," she added.

"It already looks like he has been beaten up. It is time now for the British government to get involved and help secure Aiden's release because he is still a British citizen," she said.

London is aware that a British citizen is detained and is in contact with his family, said a source aware of the matter, stressing that the current situation in Ukraine seriously restricts Britain's ability to obtain information and provide consular assistance.

"I'm in bits. My son will be scared, just as we are," Wood told the Telegraph.

In videos circulating on social media and carrying the logo of Kremlin-backed broadcaster RT, the young man appears to imply that Ukraine is prolonging the conflict.

His grandmother, Pamela Hall, slammed the clips as "propaganda," Britain's domestic Press Association reported.

The newspaper reported that Aslin, known by his first name Johnny, joined the Ukrainian military in 2018 and bought a house in Ukraine to start a family with his fiancee.

He previously fought alongside the Kurds against the Islamic State group in Syria, the newspaper said.