The family of a British man allegedly captured by Russian forces while fighting in the Ukrainian resistance have described footage of him in captivity as “propaganda”, as they begged Vladimir Putin to “treat him with humanity”.

Images on Russian television appeared to show prisoner of war Aiden Aslin, 28, originally from Nottinghamshire, being led around in handcuffs with a cut on his forehead.

Days earlier, comments posted on his Twitter account, which is being run by a friend while he is fighting with the Ukrainian marines, said he had “no choice but to surrender to Russian forces”.

Footage shared on social media apparently showing Mr Aslin in captivity was allegedly broadcast on Russian state-controlled television channel RT, which was recently taken off air in the UK by broadcasting regulator Ofcom amid concerns it was peddling Kremlin propaganda.

It’s propaganda. Ukraine is his adopted country

Speaking dispassionately and slowly, in broken sentences, he says: “I fought in beginning, Ukraine was good side.

“But then eventually I see they don’t make right decisions that would end war.”

His grandmother, Pamela Hall, told the PA news agency: “It’s propaganda.

“Ukraine is his adopted country.

“He’s engaged to a Ukrainian lady, they live together.

“He was due to get married this month, and they were talking about setting up a new home together, children – great-grandchildren in my case.”

Ang Wood, the Briton’s mother, called on the Kremlin to treat her son as a prisoner of war in accordance with international rules, and for the British Government to “take Putin down”.

Ms Wood told the Telegraph: “He called me and said they have no weapons left to fight.

“I love my son, he is my hero. They put up one hell of a fight. Boris (Johnson) needs to take Putin down.”

She said she recognised her son from images released in Russia due to his distinctive tattoos.

“It’s Aiden, I can’t deny it. It’s him,” she said.

“I’m in bits. My son will be scared just as we are.

“I now hold Vladimir Putin to the terms of the Geneva Convention. Aiden is a serving member of the Ukrainian armed forces and as such is a prisoner of war and must be treated with humanity.

“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.”

Mr Aslin had been defending the besieged city of Mariupol with his unit during heavy fighting in recent weeks.

But after 48 days, he said he had to surrender.

“We have no food and no ammunition,” a post on his Twitter account read.

“It’s been a pleasure everyone – I hope this war ends soon.”

The Foreign, Commonwealth and Development Office has yet to comment.

The Telegraph reported Mr Aslin enlisted in the Ukrainian army in 2018 and that he had previously fought against the so-called Islamic State in Syria.