Finland's defence ministry said on Thursday evening it suspected that a Russian aircraft had violated its airspace earlier in the day.
"Every suspected violation of air space is taken seriously," Defence Minister Antti Hakkanen said in a ministry statement. "An investigation is underway."
There have been a series of such incidents in Finland, which shares a 1,340-kilometre border with Russia.
Finland suspects two Russian military aircraft of having entered Finnish airspace in May and in June, and summoned the Russian charge d'affairs at the time.
The risk of drones drifting into Finland as a result of the ongoing war in Ukraine is rising, the head of the country's military intelligence service said in January.
