Officials attend a flag-raising ceremony after Finland's accession to NATO, at the NATO headquarters in Brussels, on April 4, 2023. (PHOTO / AFP)
Finland's embassy in Moscow has received a letter containing an unknown powder and has reported the matter to the Russian authorities, Russian news agencies reported on Friday.
Relations between Moscow and Helsinki have deteriorated sharply since Finland formally joined NATO on April 4, becoming the 31st member of the US-led military alliance. Finland shares a long land border with Russia.
The embassy received three letters on Thursday, one of which contained a powder, the RIA news agency reported.
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"In line with the security rules of the Finnish foreign ministry, the letters in question were handed to official representative organs of Russia which will study the matter," RIA quoted the embassy as saying.
The embassy said it had also informed Russia's foreign ministry of the incident.
Finland's decision to join NATO ended seven decades of strategic non-alignment which began after the country repelled an attempted Soviet invasion during World War Two. In the postwar period it opted to maintain friendly ties with Moscow.
But the Russia-Ukraine conflict that started in February 2022 prompted Finns to seek security under NATO's collective defence pact, which states that an attack on one member is an attack on all.