The construction of barbed-wired fence along Finland’s long border with Russia - primarily meant to curb illegal migration - has broken ground near the southeastern town of Imatra less than two weeks after the Nordic country joined Nato as the 31st member of the military alliance.

The Finnish Border Guard on Friday showcased the building of the initial 3km stretch of the fence to be erected in Pelkola near a crossing point off Imatra, a quiet lakeside town of some 25,000 people.

Finland’s 1340km border with Russia is the longest of any European Union member.

Construction of the border fence is an initiative by the border guard that was approved by Prime Minister Sanna Marin’s government amid wide political support last year. The main purpose of the 3m high steel fence with a barbed-wire extension on top is to prevent illegal immigration from Russia and give reaction time to authorities, Finnish border officials say.

Finnish border guards stay at construction site of the border barrier fence between Finland and Russia near Pelkola border crossing point in Imatra, south-eastern Finland. Photo / AP

In 2015-2016, Moscow attempted to influence Finland by organising large numbers of asylum-seekers to go to northern Finnish crossing points in the Arctic Lapland region. Russian authorities were seen deliberately ushering thousands of asylum-seekers - mostly from Iraq, Afghanistan and other Middle East nations - to those border crossing points.

The move was seen as a show of muscle by Moscow. The issue was settled when then Finnish President Sauli Niinistö held talks with Russian President Vladimir Putin. The flow of migrants stopped shortly thereafter.

This is a scenario that Finland - a nation 5.5 million people that officially became a Nato member on April 4 - wants to prevent from repeating itself.

Border officials are quick to acknowledge, however, that it was Russia’s invasion of Ukraine on February 24 last year - the main reason for Finland’s quick push to join Nato after decades of military nonalignment - that prompted construction of the border fence.

 “Border barrier fence was no kind of political topic before the war (in Ukraine). And actually, it wasn’t a kind of plan of the Finnish border guard,” Brig. Gen. Jari Tolppanen, head of the technical division at the Finnish Border Guard, told The Associated Press. “All changed after the attack (of Russia against Ukraine).”

The pilot section of the fence is scheduled to be completed by this summer, while the barrier will eventually be extended to a maximum of 200km. It will cover areas - in bits and pieces of separate length - mainly in southeastern Finland near the main border crossing points with Russia but it will also have sections up in the Arctic north in Lapland.

“In this new situation, we must have much more credible and much more independent border control,” Tolppanen said. “We need to strengthen our resources. And the fence is necessary in order to manage, for example, large-scale illegal immigration.”

Imatra is located a mere 7km from the Russian industrial town of Svetogorsk in the Karelia region and is a few hours’ drive away from Russia’s second city of St Petersburg. The town has a long history in dealing with Russians - tourists, day-trippers and permanent residents alike.

“Here in Imatra, we’re not so afraid about Russians because the border has always been there and it has never been open like between European countries,” said Antero Lattu, vice chairman of Imatra City Council. He stressed that locals aren’t afraid of Russians “but we’re happy because of that fence.”

Border guards near the Pelkola border crossing point in Imatra, south-eastern Finland. Photo / AP

Erkki Jouhki, who works as a town planner, agreed but also stressed Finland’s military capabilities. Nato membership gives Finland “a strong back but we have a very strong army. it’s very well (armed) ... it’s a very modern army here because of Russia.”

The border fence project is estimated to cost a total of 380 million euros ($422 million) and is scheduled to be completed by 2026.

Finland’s long eastern frontier runs mainly through thick forests. In some places the Finnish-Russian border is marked only by wooden posts with low fences meant to stop stray cattle.