Slovakia has charged a former military academy officer and another man with espionage for Russia, police and a special prosecutor said on Tuesday.
The announcement comes a day after the NATO country expelled three Russian diplomats. Russia said it would respond to what it called an unjustified expulsion.
Acting police president Stefan Hamran told a news conference in Bratislava, shown live on television, that police had detained and charged a former vice-rector at a military academy, identified as Pavol B., with cooperating with Russian military intelligence GRU since 2013.
"This person was intelligence contact of Russian GRU officers ... for whom he sought, collected and divulged information of strategic importance, Hamran said.
Hamran identified the other man as Bohus G., a contributor of a website shut down by government earlier this month for spreading disinformation.
He had admitted to seeking information from classified intelligence reports for parliament, Hamran said.
The accused could face between 4 to 13 years in prison if proven guilty. Two other people were detained but released without charge, police said.
Special prosecutor Daniel Lipsic said Russia's attack on Ukraine has brought renewed focus to espionage activities.
"The Russian Federation has classified Slovakia as unfriendly state and for this reason, these cases will receive large attention," he said.
(Reporting by Jan Lopatka Editing by Raissa Kasolowsky)