Estonia has told the head of its branch of the Russian Orthodox Church to leave the country, calling him a threat to national security, Estonian public broadcaster ERR reported on Thursday.

Valeri Reshetnikov, who heads the Estonian Orthodox Church of the Moscow Patriarchate as Metropolitan Eugene, was refused an extension of his residence permit and will have to leave by Feb. 6, ERR said, citing the country's Police and Border Guard spokesperson.

The Estonian government has repeatedly asked Reshetnikov to "stop vindicating the Kremlin regime and Russia's military actions in his statements" but he failed to do this, the spokesperson said.

Neither the Russian Orthodox Church nor Estonian authorities were immediately available for comment.

Estonia and its Baltic neighbours Latvia and Lithuania are among the staunchest supporters of Ukraine as it battles Russia's invasion. All three Baltic states were ruled by Moscow for decades during the Soviet era and today are members of NATO and the European Union, which Ukraine also aspires to join.

In largely secular Estonia, the Orthodox Church, favoured by its sizeable ethnic Russian minority, is the most widespread religion, with 16% of the population affiliated with it.

Ethnic Russians make up nearly one quarter of Estonia's 1.3 million-strong population, the country's 2021 census showed.

The Lutheran Church, which is favoured by Estonians, is in second place, with eight percent of the population affilated.

Earlier this week, the Estonian Internal Security Service said it had detained a Russian citizen who is a professor at Tartu University on suspicion of spying for Moscow.