Sweden says four Russian fighter jets briefly violated its airspace.
The incident occurred over the sea east of the Baltic island of Gotland on Wednesday, the Swedish Armed Forces said.
Fighter jets from the Swedish Air Force documented the incident, which involved two Russian SU-27 and two SU-24 jets. "This is an unprofessional and irresponsible action on the part of Russia," said Air Force Chief Carl-Johan Edström.
Sweden and neighbouring Finland are not members of NATO, but are close partners of the military alliance.
The two countries held a joint military exercise in the Baltic Sea on Wednesday against the backdrop of the war in the Ukraine that has put Europe on edge. According to Sweden, fighter jets and warships were involved in the exercise.
