Finland's embassy in Moscow has received a letter containing an unknown powder and has reported the matter to the Russian authorities, Russian foreign ministry spokeswoman Maria Zakharova said on Friday.
Relations between Moscow and Helsinki have deteriorated sharply since Finland formally joined NATO on April 4, becoming the 31st member of the U.S.-led military alliance. Finland shares a long land border with Russia.
The embassy informed Russia's foreign ministry that it had received three letters on Thursday, at least one of which contained a powder, Zakharova said.
"We can confirm such an appeal from the embassy of Finland to the Russian foreign ministry, according to which three identical envelopes addressed to the military attache and his aides were delivered on April 13 to the diplomatic mission's mailbox," she said.
"The embassy of Finland will be informed of the results of the inquiry."
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 Russia's invasion of Ukraine 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.
(Reporting by Reuters; Editing by Gareth Jones and Josie Kao)
