The high court of the self-proclaimed Donetsk Republic on Thursday sentenced to death two British “mercenaries” and a Moroccan who fought for Kyiv in the Ukrainian war, Russian news agencies reported.

The settlement in the Donbass region in eastern Ukraine has the support of Moscow but is not recognized by any other country or international organisation. According to Tass, the court said the trio had one month to appeal the decision or request “payment” to change the sentence.

However, family members of Aiden Aslin, 28, from Nottinghamshire, and Shaun Pinner, 48, from Bedfordshire, claim that they are not “mercenaries” but are part of the official Ukrainian military. That’s why they consider them “prisoners of war”. In addition to the two, Saudun Brahim of Morocco was sentenced to the same sentence.

In an interview with “The Guardian” and “BBC”, family members said the process was “a demonstration conducted in complete violation of the Geneva Prisoners of War Convention”.

After the verdict was announced, Boris Johnson government spokesman said London was “deeply concerned” by the conviction.

“We repeatedly say that they are prisoners of war, cannot be used for political purposes, and that they have immunity under the Geneva Convention.

“We continue to work with the Ukrainian authorities to ensure that every British citizen is treated as a prisoner of war.”

Shortly thereafter, Justice Minister Liz Truss expressed her “total condemnation” of the sentencing of Aslin and Pinner, adding that both were “responding to a legitimate and illegitimate process”. “My thoughts are with them and their families, and we will continue to do everything we can to support them.”

Several former military and international volunteers have joined Ukrainian forces to defend the country since the start of the war with Russia. But this is the first conviction of its kind in the conflict that lasted more than 100 days.