The decision to imprison him for 13 years was taken by the so-called supreme court in Russian-occupied Luhansk in Ukraine, for a crime that evidence has shown Mr Butkevych could not have committed.

“A court in Moscow has upheld the decision made during a sham trial which was held in secret, against a defendant who had limited contact with the outside world, including his lawyer, and was apparently forced to incriminate himself on video for a crime which Maksym Butkevych simply could not have committed,” Denis Krivosheev, Amnesty International’s deputy regional director for research, Eastern Europe and Central Asia said.

Before the war in Ukraine, Mr Butkevych led a Ukrainian NGO helping refugees find protection in Ukraine. Following Russia’s invasion of Ukraine, he volunteered for the Ukrainian Armed Forces before being put in charge of a platoon. His unit was later captured on the front line by Russian forces.

Mr Krivosheev said: “Since his capture, Maksym Butkevych has been heavily smeared by the Russian media and the Russian authorities in Moscow and portrayed as a villain intent on killing civilians. Wilfully depriving Maksym Butkevych, as a prisoner of war, of fair trial rights constitutes a war crime in itself.

“The sham trial against Maksym Butkevych and his treatment since his captivity is a reprisal by Russia for his civic activism and his prominent human rights work, and so is the outcome of the appeal hearing, which should have quashed the 13-year sentence and ordered his immediate release from custody.

“In contravention of international humanitarian law, Russia has consistently denied the ICRC unimpeded and repeated access to all prisoners of war, despite its own persistent demands and those of the UN and other stakeholders. It has wilfully deprived Ukrainian prisoners of war of the right to a fair and regular trial, which constitutes a war crime, and those responsible must be brought to account.

“Russia must fully abide by international law governing occupation. It must end immediately its war or aggression against Ukraine. For all victims of all crimes under international law committed by its forces in Ukraine, Russia must provide full and adequate reparation.”