Moscow accused Poland and Finland of threatening its security on Wednesday and vowed a response to multiplying "threats" on Russia's western frontier from NATO members.
Poland, Ukraine's staunch ally and neighbour, has strengthened security on its border with Belarus after Minsk became a new base for Russian Wagner fighters.
Finland, which shares a long border with Russia, joined NATO in April in a historic move fuelled by Moscow's Ukraine offensive.
"Threats to the military security of the Russian Federation have multiplied in the western and northwestern strategic directions," Russian Defence Minister Sergei Shoigu said at a meeting with military officials.
Those risks "require a timely and adequate response," he added.
"We will discuss the necessary measures to neutralise them at the meeting and make appropriate decisions."
He singled out Poland, which he said was being "militarised" and used by the United States "as the main instrument of anti-Russian politics".
Warsaw announced Wednesday it would send an additional 2,000 troops to its eastern border to join the 2,000 soldiers already stationed there.
The NATO member last week said Belarusian helicopters had violated its airspace and has warned of provocations from Belarus.
Shoigu said the Polish troops would be in "the immediate vicinity of the borders of the Union State," referring to an alliance between Moscow and Minsk.
President Vladimir Putin said last month that Moscow would respond to any aggression against Belarus "with all the means at our disposal".
Shoigu also said that "a serious destabilising factor is Finland joining NATO, and in the future -- Sweden."
Last month, Turkey dropped its opposition to Sweden entering NATO, greenlighting Stockholm's accession aspirations.
The Kremlin has said that Sweden joining NATO would jeopardise Russia's security and said it was planning countermeasures.
Sweden shares a short Arctic border with Russia.
