Denmark says drones flown over its airports appear to be the work of a "professional actor" but there was no evidence of Russian involvement, after such activity disrupted its airspace for the second time in a week.

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

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

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.

Estonia is building fortifications along its border with Russia and military officials warn NATO is facing growing threats from Moscow.

Russian unmanned aerial vehicles (drones) and fighter jets have repeatedly violated NATO, the North Atlantic Treaty Organization, airspace in recent days, sharply escalating tensions in Europe. Large drones have appeared over major airports and military bases,

NATO Secretary General Mark Rutte says NATO has trained and prepared for incursions into its airspace for decades and is assessing whether the recent violations were intentional. He speaks with Bloomberg Editor-in-Chief John Micklethwait on Bloomberg Television.