Aleksandrs Krasnopjorovs, an ethnic Russian and former Soviet Red Army soldier who served in Afghanistan during the 1980s, worked for Latvian state railways and had access to its network of surveillance cameras.

He was found guilty of recording videos of NATO troops and cargo being moved by rail -- images considered to be classified -- and then sending them to contacts in Russia.

Krasnopjorovs pleaded not guilty and his lawyer vowed to appeal the verdict.

Latvia hosts one of four NATO battle groups deployed to the three Baltic states and Poland to reinforce the alliance's eastern flank, particularly since Russia's annexation of Crimea from Ukraine in 2014.

Krasnopjorovs made the recordings between October 2015 and September 2016 when troops from Canada, Poland, United States and other NATO member countries arrived in Latvia along with heavy equipment that was transported mostly by rail.

Krasnopjorovs, who lost his railway job after being arrested in late 2016, spent more than a year in pre-trial detention and so will now only be required to serve three months of the sentence he was handed on Tuesday.

Along with the jail time, the court also sentenced him to 60 hours of community service and 18 months probation, plus covering the court expenses. He was also found guilty of possessing explosives.

The conviction is the first of its kind after Latvia tightened legislation on what constitutes espionage and treason or terrorist activity in the wake of Crimea's annexation.

A Baltic eurozone and NATO state, Latvia has a large ethnic Russian minority accounting for about a quarter of its 1.9 million people.