Unidentified drones forced the temporary closure of Denmark’s Copenhagen Airport and Norway’s Oslo Airport on Monday evening, disrupting air traffic across the Nordic region. Operations at both facilities halted for several hours, with flights diverted and tens of thousands of passengers stranded.

Danish Prime Minister Mette Frederiksen described the drone activity as an attempt to “disrupt and create unrest,” calling it the most serious attack on Danish critical infrastructure to date. She emphasized that authorities were not ruling out any possibilities regarding the perpetrators, linking the incidents to recent patterns of drone incursions, airspace violations, and cyberattacks targeting European airports.

Norwegian state media released footage of the large, unidentified drones, which caused nearly four hours of chaos. In comments to public broadcaster DR, Frederiksen cited suspected Russian drone incursions into Polish and Romanian airspace, as well as reports of Russian fighter jets entering Estonian airspace. Earlier this month, Polish officials stated they had shot down Russian drones violating their airspace during an attack in western Ukraine.

Ukrainian President Volodymyr Zelenskiy referenced “Russia’s violation” of NATO airspace in Copenhagen on September 22, though he did not provide a source for the claim. Danish police confirmed no immediate evidence connecting the drone incidents in Norway and Denmark, while Copenhagen Airport stated its airspace was closed at around 20:30 local time due to the unidentified aircraft.

EU and NATO leaders have yet to publicly attribute the attacks. Authorities reiterated their commitment to investigating the incidents but stopped short of confirming the origin of the drones.