Four Russian fighter jets briefly violated Swedish territory over the Baltic Sea, the Swedish Armed Forces said Wednesday, sparking swift condemnation from the country's defense minister.

Two Russian Su-27 and two Su-24 fighter jets briefly entered Swedish airspace east of the Swedish island of Gotland in the Baltic Sea, Sweden's Armed Forces said in a statement, adding that Swedish JAS 39 Gripen jets were sent to document the violation.

"The Russian violation of Swedish airspace is of course completely unacceptable," Defense Minister Peter Hultqvist told news agency TT. "It will lead to a firm diplomatic response from Sweden. Swedish sovereignty and territory must always be respected."

Sweden's Armed Forces said the situation was under control and that the incident showed preparedness was good.

"This is an unprofessional and irresponsible action on the part of Russia," said Air Force Chief Carl-Johan Edström.

Sweden and neighboring 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 Ukraine that has put Europe on edge. According to Sweden, fighter jets and warships were involved in the exercise.

Sweden said Sunday it would send military aid, including 5,000 anti-tank weapons to Ukraine, the first time since 1939 that Sweden has sent weapons to a country at war.