Britain strongly condemned on Wednesday the sentencing of UK national James Anderson to 19 years in prison by a Russian court, which accused him of having fought for the Ukrainian army.

"We strongly condemn the sentencing of James Anderson, a British national, in a Russian court on false charges," said a spokesperson for the Foreign Office, who called on Russia to respect its obligations towards "prisoners of war".

The Russian court press service for the city of Kursk said James Scott Rhys Anderson, 22, was found guilty of a "terrorist act" and acting as a mercenary, after he was captured while fighting in the region in November.

The Kursk court released video of Anderson being led into court in handcuffs, wearing a winter hat and jacket that appeared to be prison uniform.

He nodded silently after having the sentence translated to him. He has the option to file an appeal.

Ukraine launched its shock cross-border offensive in August, the first time a foreign army took control of Russian territory since World War II.

Anderson, from the English town of Banbury, has spoken in several videos filmed by Russian officials after he was taken prisoner, saying that he went to fight for Ukraine's International Legion after being sacked from the British army.

Kursk's second western district military court spent three days on Anderson's trial with the hearings held behind closed doors, the press service said.

The court said Anderson admitted guilt and decided to take part in the "armed conflict for financial reward".

Anderson earlier told Russia's Izvestia newspaper he was paid US$400 a-month and about US$60 a day while on combat missions.

The Briton was told by the court he would spend the first five years of his sentence in a prison - where conditions are worse than in a penal colony. He would then be transferred to a penal colony with "strict" conditions. (AFP)