Finland President Sauli Niinistö and Prime Minister Sanna Marin have announced their support for Nato membership, indicating a major policy shift following decades of non-alignment.

The move comes as the Nordic country was forced to review its security situation in the wake of the Russian invasion of Ukraine. Finland shares a 1,300km-long border with Russia.

In a joint statement, the two Finnish leaders said that the country must apply to join the Nato military alliance ‘without delay’. A decision is expected to be taken in the following few days.

“Now that the moment of decision-making is near, we state our equal views, also for information to the parliamentary groups and parties.

“Nato membership would strengthen Finland’s security. As a member of Nato, Finland would strengthen the entire defence alliance,” the joint statement said.

Reuters reported that the Finnish parliament is expected to debate joining the military alliance next week. Several legislators have already announced support for the Nato bid.

The announcement drew a sharp rebuke from Russia. The news agency quoted the Russian Foreign Ministry as saying that Moscow would take “retaliatory steps, both of a military-technical and other nature, in order to stop threats to its national security arising.”

Another Finish neighbour, Sweden, is also expected to apply for Nato membership soon.

The two countries recently signed mutual security assurances with the UK to strengthen defence collaboration, as well as overall security.

US Pentagon spokesperson John Kirby said, in an interview, that integrating Finland into Nato will not be difficult.