Moscow has regularly handed out heavy sentences to those it accuses of spying for Ukraine amid its nearly three-year offensive, with such cases especially common in the Black Sea peninsula, seized by Russia from Ukraine in 2014.

The Moscow-led local prosecutor’s office said a 45-year-old unnamed man had sent the locations of Russian air defence units in the city of Kerch – on the eastern edge of Crimea – to Ukrainian intelligence in September of last year.

“The court established that the man offered cooperation to a representative of Ukraine’s security service,” the prosecutor’s office said on Telegram.

“He was found guilty of high treason”, and sentenced to 15 years, it added.

The RIA Novosti state-run news agency said the man worked on railway tracks before his arrest.

The case, as has become common practise in Russia, was heard behind closed doors.