Finland’s imminent NATO membership will force Moscow to take countermeasures, the Kremlin warned on Tuesday.

"The Kremlin believes that this is another aggravation of the situation, that NATO expansion is an encroachment on our security, the interests of the Russian Federation. This is exactly how we perceive it. We will take countermeasures to ensure our own tactical and strategic security," Kremlin spokesman Dmitry Peskov told a press briefing.

Peskov said the countermeasures that Moscow "deems necessary" will be taken, adding that the Russian Armed Forces will report on the response to NATO actions in Finland.

"Believe me, our military will inform us about everything in a timely manner … We will carefully observe what happens in Finland, how the North Atlantic bloc will exploit the territories in Finland in terms of placing weapons, systems, and infrastructure that will be close to our borders and potentially threaten us. Depending on this, measures will be taken," he said.

Reversing its longstanding policies, Finland announced its intention to join NATO soon after Russia started its war on Ukraine in February 2022 – a war launched in part to prevent any move by Ukraine to join NATO.

As Finland joins NATO with its 1,340-kilometer (832-mile) frontier with neighboring Russia, NATO’s border with Russia is being roughly doubled.

‘Lost its special voice’

Separately, the Russian Foreign Ministry said in a statement that NATO has taken another step closer to the country, and that the situation in northern Europe has changed radically.

The statement said that Finland’s policy of military non-alignment before last year was "a conscious choice" taken by Finnish leaders after World War II that showed “wisdom.”

“By joining NATO, Finland finally renounced its self-identity and any independence, which has distinguished it in international affairs for decades … Finland has become one of the small, undecided member countries of the alliance, having lost its special voice in international affairs,” the statement said.

Saying that Finland’s policy of military non-alignment has long served Helsinki’s national interests, the statement underlined it has also been “one of the important factors for ensuring confidence in the Baltic Sea region and on the European continent as a whole.”

“We are convinced that history will judge this hasty step taken by the authorities of this country without due regard for public opinion by organizing a referendum and carefully analyzing the consequences of NATO membership. Finland's accession to NATO cannot but have a negative impact on Russian-Finnish bilateral relations,” the statement concluded.​​​​​​​

NATO Secretary General Jens Stoltenberg said on Monday that Finland will become a full-fledged member of the alliance on Tuesday, with its flag raised at NATO headquarters.​​​​​​