Finland joined NATO to become the alliance's 31st member on Tuesday, issuing a major rebuke to Moscow and doubling the border length Russia shares with the military alliance.

Russian President Vladimir Putin's invasion of Ukraine spurned Finland to join the military alliance last year. Both Finland and Sweden filed to join NATO, though Sweden's process is still ongoing.&nbsp;

<i>This is a developing story. Check back soon for updates.</i>

<div class="author-bio"><p>Anders Hagstrom is a reporter with Fox News Digital covering national politics and major breaking news events. Send tips to Anders.Hagstrom@Fox.com, or on Twitter: @Hagstrom_Anders.</p></div>

Finland officially joined NATO on Tuesday, becoming the military alliance's 31st member. The move is a major rebuke to Russia, which has long opposed NATO expansion.

Finland joins NATO in major setback to Russia

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