Aalborg Airport in northern Denmark was shut down Wednesday evening after unidentified drones were spotted over its airspace, just two days after similar incidents closed Copenhagen Airport.

Police confirmed flights were diverted as they investigated, though the number and origin of the drones remain unknown.

The repeated disruptions have fueled suspicions of Russian involvement, with Ukrainian President Volodymyr Zelensky warning the incursions are part of Moscow’s provocations against NATO states.

Danish police said the drones appear to be operated by a “capable actor,” and the country’s intelligence agency has already declared a high risk of sabotage, the U.S. Sun has reported.

Analysts suggest the incidents may be part of a broader Kremlin strategy to test Europe’s defenses, coinciding with recent cyberattacks on major airports across the continent.