A military court in Moscow has sentenced a Russian officer to seven years in prison for spying for Poland.
Prosecutors said Maj Yurenya had tried to infiltrate the FSB
Maj Sergei Yurenya was put on trial in August, accused of selling military secrets to Polish secret agencies.
The Federal Security Service (FSB) said Maj Yurenya had provided Poland with intelligence on military units in central Russia.
Poland and Russia engaged in tit-for-tat expulsions of diplomats accused of spying in 2000.
The FSB said Maj Yurenya had been recruited by Polish secret services in 2005-2006 and subsequently provided them with accurate information on the staffing and movement of military personnel in the Moscow Military District, an area covering 700,000 sq km (430,000 sq miles).
Maj Yurenya was arrested in March this year "while performing a new Polish assignment to infiltrate into FSB ranks", military prosecutor Ramil Shakurov told the RIA Novosti agency.
Relations between Poland and Russia have been tense since the collapse of the Warsaw Pact in the early 1990s, with Moscow opposing Poland's accession to Nato in 1997.