Finland says it is investigating whether Russia has recently interfered with global positioning system (GPS) signals in the northern Finish region of Lapland during NATO war games, endangering civilian air traffic.
Prime Minister Juha Sipila made the announcement on November 11, days after Finland's air-navigation services issued a warning for air traffic due to a large-scale GPS interruption in the north of the country.
Neighboring Norway issued a similar warning about loss of GPS signals for pilots in its own airspace at the end of the October, when NATO's massive Trident Juncture military exercise kicked off.
"It's possible Russia was behind the interference," Sipila said in an interview on YLE Radio Suomi. "We're now investigating it and will react accordingly."
"It's no small matter, since civilian flights have been put in danger," he also said, adding that the incident should be taken as seriously as "airspace violations."
Trident Juncture -- NATO's largest since the end of the Cold War -- involved all 29 members of the Western alliance, plus partners Finland and Sweden.
The two-week war games took place close to Russia, in an area stretching from the North Atlantic Ocean to the Baltic Sea, amid persistent tension between the West and Moscow.
NATO said the drills mustered 50,000 troops, 250 aircraft, and around 65 ships in what Secretary-General Jens Stoltenberg called a "strong display" of its capability, unity, and resolve at a time of growing danger in Europe.
The exercise drew criticism from Moscow, which seized Crimea from Ukraine in 2014 and backs separatists in an ongoing conflict in eastern Ukraine but accuses the alliance of provocative behavior near its borders.
Finland, which shares a 1,340-kilometer-long border with Russia, has recently developed closer ties with NATO but stopped short of full membership.