Drones flew over four Danish airports overnight Wednesday into Thursday, the latest instance of unexplained drone activity that has raised concerns about security in northern Europe amid growing Russian aggression.

Danish Prime Minister Mette Frederiksen linked the drone incident that shut Copenhagen airport late on Monday to suspected Russian drone activities across Europe, without providing evidence.

COPENHAGEN: Denmark has told its NATO allies that drone incursions which disrupted two airports this week were linked to a state actor, Latvia’s foreign minister said on Thursday (Sep 25), as Copenhag

Numerous drones have reportedly breached Danish airspace this week, causing disruptions at multiple airports throughout the country Drone sightings have been reported at major airports in the country,

Aalborg airport, a major commercial and military hub, was closed for three hours. Police are investigating the seemingly coordinated incident.View on euronews

It wasn’t immediately clear who was behind the flyover. But Denmark’s prime minister and NATO’s secretary-general said Tuesday that Russian involvement couldn’t be ruled out.

The alliance is rethinking how it responds to nontraditional threats after drones recently appeared in the skies over Poland and Denmark.