The 51-year-old was arrested a year ago on suspicion of planning acts of sabotage in the city of Wrocław.
A Polish court sentenced a Ukrainian national on Friday to eight years in jail for planning acts of sabotage and arson on behalf of Russia.
The court in the southwestern city of Wrocław found that the 51-year-old, named Serhyi S, had been part of a criminal ring and had made plans to set fire to various structures in the city.
The man was arrested by Polish state security officers in January 2024. The Polish Internal Security Agency alleged that he was preparing to set fire to a US-owned paint factory, among other targets.
The man denied the charges but admitted to agreeing to commit arson in return for money from an unknown party he communicated with online.
Four other people have been charged in the case, while more than a dozen others of Polish, Ukrainian and Belarusian citizenship have been arrested in connection with other planned acts of sabotage or espionage in the central European country.
Warsaw says Russia is targeting it as part of a hybrid warfare campaign against countries that have offered their support to Ukraine during the Kremlin's ongoing full-scale invasion of its western neighbour.