Russia would regard Finland joining Nato as a threat, according to a Kremlin spokesperson, after Finland's President and Prime Minister announced that they want the country to join Nato as soon as possible.
Wire services reported that Dmitry Peskov said on a conference call with media that Finland's expected application was viewed by Russia as a threatening move.
"Definitely. NATO expansion does not make our continent more stable and secure," said Peskov, according to Reuters.
He declined to elaborate on Russia's likely response.
"Everything will depend on how this expansion process of Nato expansion plays out, the extent to which military infrastructure moves closer to our borders."
The Russian foreign ministry described Thursday's statement as a "radical change in foreign policy" by the Finnish leaders. In a statement on its website, the ministry said that Finland should take into account the repercussions of this decision.
"Joining NATO will be resulted in a serious damage to Russian and Finnish bilateral relationships, stability and security in the region of northern Europe," read the statement. "Russia will be forced to take counter steps of a military-technical nature and others because of the threat to Russian national security."
Nato countries, on the other hand, have welcomed Finland's decision, with Estonian Prime Minister Kaja Kallas first to tweet her response.
“History being made by our northern neighbours,” said Kallas. "You can count on our full support. We support a rapid accession process. From our side we will make necessary steps quickly."
Michael Roth, who chairs the German parliament's foreign policy committee, told Yle that Finland joining Nato would increase security in Finland and Europe.
"It is ironic from a historical perspective that Putin, who tried to weaken Nato, made it stronger and more united than ever," said Roth.
In a television interview on Thursday, Pentagon spokesman John Kirby told MSNBC that Finland's entry into the NATO would be historic, adding it would not be difficult to integrate the country into the military alliance.
Nato Secretary-General Jens Stoltenberg said the Finns would be "warmly welcomed" and promised an accession process that would be "smooth and swift". Finnish membership would boost both Finland's security and that of the alliance, he said.