Estonia is expelling a Russian diplomat who has been accused of interfering in the country’s judicial process by “acquiring documents from a criminal case and contributing to their publication on Russian social media.”

In an announcement on Tuesday, the Estonian Ministry of Foreign Affairs said it had summoned the Russian Chargé d'Affaires to inform them that their colleague — an embassy staff member with diplomatic status — had been declared persona non grata.

The status of persona non grata (Latin for “unwelcome person”) is defined by the Vienna Convention on Diplomatic Relations, and obliges the recipient to leave the host state or be stripped of their diplomatic immunity.

Swiss newspapers have reported that Russian intelligence officers working under diplomatic cover who have been expelled by their host states have, instead of returning to Moscow, regularly traveled to Switzerland where they have continued in their efforts targeting European states.

European governments have expelled potentially hundreds of Russian spies working under diplomatic cover since the invasion of Ukraine in February 2022. The head of the British domestic security service MI5 claimed that of the 600 diplomats made persona non grata across the continent, 400 of them were spies.

In a statement regarding the expulsion, Estonia’s Minister for Foreign Affairs Margus Tsahkna accused the Russian embassy of having “interfered in the internal matters of Estonia in an unacceptable way.”

He added: “I would also like to emphasize that the coordinated actions of Russia's special services against the Republic of Estonia, including hybrid operations targeting our security, are unacceptable and must end.”

The Estonian government did not identify the court case which the Russian diplomat was accused of interfering in. 

“Estonia will discuss the matter with its partners and allies, and is prepared to implement additional measures where necessary, in order to defend our society and our values,” the Ministry of Foreign Affairs said.

“We will not tolerate nor accept any interference in Estonia's internal matters and will respond to these kinds of situations in a quick and concrete manner,” added Tsahkna.

“By expelling the diplomat, we are demonstrating that Estonia will not allow any actions orchestrated by a foreign state on its territory.”

The expulsion follows the arrest earlier this year of a university professor in the Estonian city of Tartu who was suspected of sharing information with Russian intelligence handlers during regular trips to Russia over the course of several years.

Estonia’s Internal Security Service (Kaitsepolitseiamet or KAPO) has been credited for conducting almost half of all counterintelligence convictions in Europe between 2011-2021, according to a report by Sweden’s Defence Research Agency.

An analysis by the International Centre for Defence and Security, partly written by Estonia’s prosecutor general, suggested these convictions were not a product of a greater focus on Estonia by Russia, but were likely due to the Estonian security services’ competence.