In addition to the Swede, three men from Great Britain and one from Croatia were also convicted.
More specific reasons for the verdict are missing. The men deny wrongdoing.
The trial against the five men began in the partially Russian-occupied Donetsk in August 2022. Only a month or so later, however, they were released in a prisoner exchange. The Swedish man must then have returned to Sweden.
The court that sentenced the men is located in the Russian city of Rostov-na-Donu near the border with Ukraine.
TT has asked the Ministry of Foreign Affairs for a comment.