Moscow: Russia on Thursday warned Sweden and Finland against joining NATO and said that it would add "more than double" its troops in Russia's Western flank.

Deputy chair of Russia's Security Council, Dmitry Medvedev, gave the warning and in a statement on Telegram on Thursday wrote that ground and air defence forces would be beefed up, reported CNN News.

"It will no longer be possible to talk about any non-nuclear status of the Baltic -- the balance must be restored, Medevedev added referring to the possibility of Sweden and Finland joining NATO.

Medvedev, who served as president of Russia from 2008 to 2012 in a four-year interregnum for Russian President Vladimir Putin's two-decade rule, has been aggressive in recent months, though he is not a top decision-maker.

Moreover, a 2018 Federation of American Scientists report concluded that Russia may have significantly modernized a nuclear weapons storage bunker in Kaliningrad, an exclave of Russian territory between Poland and the Baltic states, reported the news channel.

Thursday marks 50 days since the Russian invasion of Ukraine, and there has been a marked shift in Moscow's approach. Ukrainian officials have warned for days they expect a major offensive by Russian forces in the eastern Donbas region.