Russia's decision to invade Ukraine "showed that they are ready to attack an independent neighboring country," Finnish President Sauli Niinistö told CNN as he explained Finland's decision to apply for NATO membership, a US-led military alliance.

While he does not believe that Russia can attack Finland now or in the future, Niinistö said that the divided political landscape of Europe and the world does not leave much room for the disengaged, the Telegraph reports.

And while informing Russia of Finland's decision to apply for NATO membership, Niinistö said he was surprised by President Vladimir Putin's calm reaction.

"In fact, the surprise was that he took it so smoothly," he was quoted as saying by CNN.

"But in security policy, especially in talks with Russia, you have to keep in mind that what he said does not mean that you do not have to be aware all the time (in the future)."

"But so far, there do not seem to be any immediate problems (that may arise)," he added.

Niinistö also said that while he was "surprised" by Turkish President Recep Tayyip Erdogan's comments, he was "not worried" about Turkey's blocking of Finland's NATO membership.

"I believe there will still be a lot of discussion and I'm not that worried about that," he told CNN.