Sweden says Russian fighter jets briefly entered its territory over the Baltic Sea on Wednesday.
The Swedish Armed Forces says two Russian SU 27s and two Russian SU 24s flew east of Gotland, a Swedish island.
"With the current situation as backdrop, we take this incident very seriously. Russia's conduct is unprofessional and irresponsible," said Air Force Commander Carl-Johan Edström.
Sweden says it was conducting an operation with its rapid readiness unit when it noticed the Russian jets.
"This demonstrates that our readiness is good. We were on site to secure Sweden's borders and territorial integrity. We are in full control of the situation," Edström said.
The Swedish Defense Minister went a step further and criticized Russia for its actions.
"The Russian violation of Swedish airspace is of course completely unacceptable," Defense Minister Peter Hultqvist told news agency TT, according to Reuters. "It will lead to a firm diplomatic response from Sweden. Swedish sovereignty and territory must always be respected."
Europe is on high alert following the Russian invasion of Ukraine. While countries have expressed support for Ukraine, they don't want the situation to grow and spill over into other countries.