The ministry said in a short statement that the alleged violation took place Wednesday morning on the Baltic Sea near the town of Porvoo, east of Helsinki. It provided no further details and said the Finnish Border Guard is investigating the matter.
Spokesman Kristian Vakkuri separately told Finnish newspaper Iltalehti that the alleged violation by a Russian aircraft lasted for about two minutes, entering about one kilometer (0.6 miles) into the airspace of Finland, which is not a member of NATO.
It was the second reported air violation of Finland's airspace this year.
In April, the Portuguese Air Force said one of its surveillance planes unintentionally strayed into Finnish airspace during a NATO mission over the Baltic Sea.
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