Kremlin vows countermeasures, calling Helsinki's move 'assault' on its security

The flag of Finland was raised at the NATO military alliance headquarters in Brussels on Tuesday as the country became the group's 31st member.

The addition of Finland, the first new member since North Macedonia in 2020, came after the quickest-ever accession process, and means that land borders between NATO member states and Russia have now doubled, as it shares a 1340-kilometer frontier with the Eastern European superpower.

The Kremlin on Tuesday branded Finland's NATO membership an "assault on our security" and said it would take countermeasures.

"The expansion of NATO is an assault on our security and Russia's national interests," Kremlin spokesman Dmitry Peskov told reporters in Moscow.

"And this forces us to take countermeasures... in tactical and strategic terms." He did not provide further details.

Both Finland and neighbor Sweden previously had a history of nonalignment but were moved to apply for membership following the outbreak of the conflict in Ukraine a year ago.

Membership applications have to be unanimously approved, and Turkiye was the last member to agree to Finland joining, after expressing concerns over the activities of people who oppose the Turkish government who are living in Sweden and Finland. Sweden's application has yet to be approved, although it is hoped that process will be completed in the summer.

All that remained were Tuesday's highly choreographed formalities at NATO headquarters.

Finland's joining of the group was sealed when the country's Foreign Minister Pekka Haavisto handed over accession papers to United States Secretary of State Antony Blinken, coincidentally on the 74th anniversary of NATO being founded.

"Not so many years ago we thought it was unthinkable that Finland would become a member. Now they will be a full-fledged member of our alliance and that is truly historic," NATO Secretary-General Jens Stoltenberg said.

Blinken said Finland's membership sends a message to Russia.

Potent military

Finland stayed out of NATO throughout the Cold War.

Now its membership brings a potent military into the alliance with a wartime strength of 280,000 and one of Europe's largest artillery arsenals.

And its strategic location bolsters NATO's military power on a border running from the Baltic states to the Arctic.

Moscow also replied with Deputy Foreign Minister Alexander Grushko saying that Russia would bolster military forces in its west and northwestern regions, if it felt the need.

If "forces and resources of other NATO members are deployed in Finland, we will take additional steps to reliably ensure Russia's military security," he explained.

NATO membership after so many years of nonalignment completes a flurry of political activity in Finland, after a general election at the weekend that saw left-wing Prime Minister Sanna Marin, who was a strong supporter of the membership application, beaten, although the election campaign was largely fought on domestic issues, with NATO membership being supported across the political spectrum.