Four Russian military planes violated Swedish airspace on Wednesday, according to information provided by the Swedish Defence Forces.
Swedish broadcaster SVT reported that two Sukhoi SU-27 and two Sukhoi SU-24 fighter jets entered Swedish airspace east of the Baltic Sea island of Gotland, adding that the incursion was short-lived.
The Swedish Air Force described the incident as being "particularly serious" given the current situation, and called the Russian actions unprofessional and irresponsible.
Russian military aircraft often violate Swedish and Finnish airspace, but the Swedish Air Force noted that the majority of these infractions are accidental.
The force said it scrambled a Jas 39 Gripen fighter jet in response to the incursion and to identify the Russian aircraft.
The incident occurred on the same day as Finnish Defence Forces took part in a joint military exercise organised by Sweden in the maritime area west of the island of Gotland.
The aim of the drill was to test and develop the interoperability of the countries' navies and air forces, a press release from the Finnish Defence Forces stated.