Finland's border guard on Friday unveiled the first section of a 200-kilometer border fence with Russia being built after Moscow invaded Ukraine last year.
Finland joined NATO just a week ago and its 1,300-kilometer border has also doubled the frontier between the U.S.-led military alliance and Russia.
Three meters tall and topped with barbed wire, it will cost around 380 million euros ($417 million) and is due to be completed by 2026.
Officials showed the construction site of the first three-kilometer section near the Imatra border crossing point in southeastern Finland.
"We started work on the site about a month ago. We have built a road and foundations," Jaakko Makela from GRK, the construction company tasked with building the first phase, told AFP.
About 70% of the fence will be erected on the southeast, with several smaller sections planned for central Finland and the largely uninhabited Arctic border in Lapland.
"Typical target areas will be border crossing points and their surrounding areas, roads leading across the border. Areas where human access is easy," Brigadier General Jari Tolppanen told reporters.
"The necessity was triggered by a change in the security situation in Europe," Tolppanen told AFP.
"There is a need to reduce dependence on the effectiveness of Russian border control."
He said the fence was "the only effective and safe way to control large-scale entry."
Some six kilometres from the construction site, locals in the border town of Imatra have mixed feelings.
"I think that is a very good thing. It would have been better if it had been done a long time ago," Sinikka Rautsiala told AFP.
But Pirjo Pankalainen said it was not "terribly necessary," adding "a lot of fear has been caused by the situation, many people feel that it is important to build it."