Two British soldiers who were captured by Russian forces while fighting for Ukraine have been sentenced to death by pro-Moscow rebels.

Downing Street said the Government was “deeply concerned” about the sentences given to Aiden Aslin, 28 and Shaun Pinner, 48, who have been found guilty of taking action towards violent seizure of power at a court in the self-proclaimed Donetsk People’s Republic.

A No 10 spokesman said: “We are obviously deeply concerned by this. We have said continually that prisoners of war shouldn’t be exploited for political purposes.

“You will know that under the Geneva Convention prisoners of war are entitled to combatant immunity and they should not be prosecuted for participation in hostilities.

“So we will continue to work with the Ukrainian authorities to try to secure the release of any British nationals who were serving in the Ukrainian armed forces and who are being held as prisoners of war.”

A third man, Moroccan national Saaudun Brahim, was convicted alongside them.

The men were accused of being “mercenaries” after fighting with Ukrainian troops.

Russian media outlet RIA Novosti reported that the three are set to face a firing squad.

Interfax, a Russian news agency, claimed the men would be able to appeal against their convictions.

It comes after the family of Mr Aslin, who is said to also hold Ukrainian nationality, shared an emotional appeal expressing their hopes for his return to the UK.

“We, the family of Aiden Aslin, wish to ask for privacy at this time from the media,” the family said in a written statement on Tuesday.

“This is a very sensitive and emotional time for our family, and we would like to say thank you to all that have supported us.

“We are currently working with the Ukrainian government and the Foreign Office to try and bring Aiden home. Aiden is a much-loved man and very much missed, and we hope that he will be released very soon.”

Mr Aslin’s MP, former Tory minister Robert Jenrick, condemned the “trumped-up charges” and said Russia had breached international law.

His comments came after footage emerged of the two men alongside Mr Brahim in what appeared to be a dock in the separatist territory’s supreme court, which is not internationally recognised.

Mr Jenrick told BBC Radio 4’s World At One programme on Wednesday: “(Mr Aslin) is a British citizen, but who also holds Ukrainian nationality, is married to a Ukrainian, joined the Ukrainian armed forces in the normal way prior to (Vladimir) Putin’s illegal invasion, and has been serving in the armed forces.

“He was taken prisoner by Russian forces and in accordance with international law and the Geneva Convention, he should be being held appropriately and returned to Ukraine at the earliest possible opportunity, possibly through a prisoner exchange.

“Instead of that, Putin’s regime have chosen to put him and another British national, Shaun Pinner, on trial on trumped up charges, no evidence whatsoever. This is, I’m afraid, a completely outrageous breach of international law and it should be condemned.”

He added: “What I hope happens is that a prisoner exchange occurs in the near future. The Russian authorities have chosen to make an example out of these two British nationals and it is, I think, completely shameful.”