A Danish helicopter is suspected of violating Finnish airspace late on Wednesday.
Finnish border guards said that the craft “briefly entered” Finnish skies near the town of Hanko in southwestern Finland.
“We do not know exactly why they were there,”said a spokesman for the Finnish Defence Ministry.
Busy above the Baltic
The area is currently hosting NATO’s international Baltops 2016 military exercises. Forces from Finland, Sweden, the US, the Netherlands, Italy, Britain and Germany are taking part in the exercise, but Denmark is not participating in the Finnish leg of the exercises.
The Danish violation comes in the wake of Russian aircraft being accused of repeatedly breaching Finnish airspace above the Baltic Sea.
The Russian foreign minister, Sergei Lavrov, has expressed his disapproval of NATO’s activities in the Baltic at a meeting in Moscow.
Finland’s border guard has begun an investigation into the incident.