Vladimir Putin’s threat has spurred on more support for Sweden and Finland to join Nato membership, polls claimed.
Despite the Russia’s threat to retaliate if the two joined the alliance, support for Nato membership has grown to 53 per cent in Finland.
The poll by Finnish broadcaster YLE also showed just 28 per cent were against Nato membership.
In Sweden, support for Nato shifted to 41 per cent for joining the alliance against 35 who were against - the first time those in favour has exceeded those against.
Finland shares a 830-mile border with Russia.
Due to the invasion of Ukraine, Matti Pesu from the Finnish Institute of International Affairs said there had been a significant shift in support to join Nato.
He said: “It’s a very significant shift. We’ve had a situation in the past 25-30 years where Finns’ opinions on NATO have been very stable. It seems now to have changed completely.”
Four Russian jets entered Swedish airspace on the island of Gotland, the country’s air force stated on Wednesday.
The Swedish were quickly scrambled to escort the jets away in what officials said was an “unacceptable” act.
Air Force chief Carl-Johan Edstrom said: “In light of the current situation we are very concerned about the incident. This is unprofessional and irresponsible behaviour from the Russian side.”
Last week, Russia warned both nations against the alliance.
Maria Zakharova, Russia’s foreign affairs spokesman, said: “Obviously, the accession of Finland and Sweden to Nato, which is primarily a military alliance as you well understand, would have serious military and political consequences, which would require our country to make response steps.”
Alexander Stubb, a former prime minister of Finland, which has been militarily neutral since the Cold War, said: "Russia is pushing Finland closer to Nato membership. Closer than ever before.
"Our security has been partially based on an option to join. At this rate, we have no other option but to join.
"Finland’s accession would strengthen the alliance and help keep northern Europe stable."
All Nato nations agreed to contribute two per cent of their GDP on defence by 2025 during a 2014 summit.
Only the US, Greece, the UK, and Poland have reached that threshold, according to the latest figures.