Finland's President Russia will respond with "military-technical and other measures" to address the national security threats arising from Finland's accession to NATO, the Russian Foreign Ministry said.
"Specific decisions regarding the buildup of defence capabilities along Russia's northwestern borders will depend on the specific terms on which Finland joins NATO, including the deployment of NATO's military infrastructure and offensive weapons on its territory," said the Ministry in a statement on Tuesday.
The lines of contact between NATO and Russia have more than doubled, constituting a major shift for Northern Europe, one of the most stable regions in the world, the Ministry noted.
"Finland's accession to NATO will have a negative effect on the bilateral relations between Russia and Finland," said the statement.
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Kremlin Spokesman Dmitry Peskov on Tuesday voiced his concerns over Finland's entry into NATO, adding that it encroaches on Russia's security and interests, Xinhua news agency reported.
"We will take countermeasures to ensure our security in tactical and strategic terms," he told a daily briefing.
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Finland on Tuesday formally became the 31st member state of NATO. The national flag of Finland was raised and the country's anthem was played for the first time at NATO headquarters in Brussels on Tuesday afternoon in a brief ceremony.
"The era of military non-alignment in our history has come to an end. A new era begins," Finland's President Sauli Niinisto said at the ceremony.
