Russia suffers major blow as Sweden officially joins NATO

• Scandinavian country joins NATO after decades of neutrality.
• Russia to take "political and military-technical countermeasures."
• Swedish public favoured joining NATO after Ukraine's invasion.

In a major blow to Russia, Sweden has officially become a member of the North Atlantic Treaty Organisation (NATO) after Swedish Prime Minister Ulf Kristersson handed over the final documents to the United States government on Thursday, Reuters reported.

The Scandinavian nation's decision to join NATO after decades of neutrality is a major shift in its security policy. For NATO, the accessions of Sweden and Finland, which share a 1,340-km border with Russia, are the most significant additions in decades.

US Secretary of State Antony Blinken said "everything changed" after Russia invaded Ukraine, citing polls showing a massive shift in Swedish public opinion on joining NATO.

He said: "Swedes realised something very profound, that if Putin was willing to try to erase one neighbour from the map, then he might well not stop there."

In response to Sweden's move, Russia has threatened to take unspecified "political and military-technical countermeasures."

While Finland joined the alliance last year, Sweden was kept waiting as Turkey and Hungary, which both have cordial relations with Russia, delayed ratifying Sweden's accession.

Turkey approved Sweden's application in January, while Hungary delayed its decision until Kristersson made a goodwill visit to Budapest in February, where the two countries agreed to a fighter jet deal.