The governments of Denmark and Sweden summoned their Russian ambassadors following reports that a Russian spy plane had entered the two countries’ airspace in succession without permission.

Danish foreign minister Jeppe Kofod made the announcement via Twitter on Sunday, claiming that the incident was “unacceptable” and “extremely worrying in the current situation,” referring to heightened tensions between Russia and the NATO countries following Russia’s invasion of Ukraine.

In a separate statement, Sweden also indicated that its ambassador would be summoned over the same flight. Swedish defense minister Peter Hultqvist claimed to local media outlets that the incursion had been “unprofessional” and “inappropriate,” particularly in light of the heightened tensions.

“There exist established protocols for this kind of case,” the Swedish foreign ministry later indicated in an email. “It concerns notably summoning the representative of the implicated nation to the foreign ministry.”

The two nations confirmed that the offending aircraft had been a Russian Antonov AN-30 propeller plane, which had been monitored by radar throughout its time over Danish and Swedish airspace. The AN-30, a derivative of the Soviet-era Antonov AN-24 passenger aircraft, is typically used for aerial reconnaissance and photography and is not usually armed.

In early March, Sweden reported a separate airspace incursion incident made by four Russian fighter jets, leading it to scramble its own jets in response.

As the Baltic Sea lies between Russia, Sweden, Finland, and NATO member states, including Denmark, its narrow band of international airspace is one of the most hotly contested areas in the world. In addition to its recent violations, Russian aircraft have also flown many non-violating sorties over the Baltic, flights which are often tracked and followed by NATO aircraft.

Moscow’s decision to invade Ukraine led to a sharp deterioration in the Kremlin’s relationship with Sweden. In the days following the onset of the “special military operation,” Sweden and Finland began parliamentary debates over whether to abandon their longstanding neutrality in foreign policy and join NATO. Formal applications from both nations are expected later in the month; NATO officials, including Secretary General Jens Stoltenberg, have suggested that the two countries would be admitted at once. Russia has protested against the two countries’ inclusion in the military alliance and indicated it could arm Kaliningrad, its exclave along the Baltic coast, with nuclear missiles in response.

Hultqvist claimed soon after the airspace violation that there was no proof connecting it to Sweden’s ongoing discussions on NATO membership.

Trevor Filseth is a current and foreign affairs writer for the National Interest.

Image: Reuters.