Finland said on Thursday that it suspects a Russian aircraft entered its airspace over the Gulf of Finland that afternoon.
According to the Finnish Ministry of Defence, the aircraft is believed to have crossed into Finnish airspace from the Baltic Sea above the western part of the Gulf of Finland.
The type of aircraft involved has not yet been identified.
Finnish Defence Minister Antti Häkkänen said every suspected airspace violation is taken seriously and that the investigation is ongoing.
There had already been a previous incident in May, when a Russian military aircraft was reported to have violated Finnish airspace. The aircraft is said to have diverted to avoid a thunderstorm over the Porkkala Peninsula between Finland and Estonia.
Finland, a NATO member state, shares a border with Russia that is more than 1,300 kilometres long.
It is the second such suspected incident in recent months.
In May, a Russian military aircraft was also suspected of violating Finnish airspace after reportedly diverting to avoid a thunderstorm over the Porkkala peninsula, between Finland and Estonia.
Finland, a NATO member, shares a border of more than 1,300 kilometres with Russia.
