HELSINKI: Alexander Stubb took office as Finland's president on Friday, ready to oversee a new era after it joined NATO in response to neighbouring Russia's invasion of Ukraine.

During his campaign for the Feb. 11 vote, Stubb said he saw no limits for Finland's participation in NATO and would be ready to let nuclear weapons be transported through Finland - though not stored there - as the country abandoned decades of military non-alignment.

"We are now facing a new era. As a result of our military alignment and NATO membership, we have taken the final step into the Western community of values, where our republic has spiritually belonged throughout its independence," Stubb said in his address to parliament during the inauguration.

Stubb listed democracy, rule of law and human rights as the core values that Finland's foreign policy would be based on under his leadership.

Stubb replaces outgoing president Sauli Niinisto, who steps down after two six-year terms in which he earned the nickname "the Putin Whisperer" for his previous close ties with the Russian leader.

"Diplomacy continues to be also an individual sport, which requires subtlety. Thus, even the smallest gets heard," Niinisto guided his successor in his farewell speech to parliament.

As an example of such diplomacy, Niinisto brought up Finland's cooperation with China in the ongoing probe into the possible role of a Hong Kong-registered cargo vessel in the damage caused to the BalticConnector gas pipeline last year.

Finnish investigators have concluded the pipeline was likely damaged by an anchor dragged across it.

"Progress has been made in investigating the matter - to everyone's surprise - not by raising voices, but by the subtle yet determined work of all participants," Niinisto said.

A day before Stubb's inauguration, Russian President Vladimir Putin said Russia must boost the troops it has deployed along its western borders with the European Union in response to Finland and Sweden joining NATO.