Finland and Sweden formally applied to join NATO on Wednesday, a decision accelerated  by Russia's invasion of Ukraine, and setting in motion an accession process that is expected to take only a few weeks, Reuters has reported. 

Sweden and Finland were both neutral throughout the Cold War, and their decision to join NATO is one of the most significant changes in Europe's security architecture for decades, reflecting a sweeping shift in public opinion in the Nordic region since Russia's Feb. 24 invasion, said the media outlet. 

"This is a historic moment, which we must seize," NATO Secretary-General Jens Stoltenberg said at a short ceremony in which the Swedish and Finnish ambassadors to the alliance handed over their application letters, each in a white folder embossed with their national flag.

"I warmly welcome requests by Finland and Sweden to join NATO. You are our closest partners, and your membership in NATO will increase our shared security," Stoltenberg said. The alliance considers that the accession of Finland and Sweden would hugely strengthen it in the Baltic Sea.

Ratification of all 30 allied parliaments could take up to a year, while Turkey says that he is against it. 

However,  Stoltenberg said on Wednesday that he thought the issues could be settled.