Denmark says 'professional actor' behind drone incursions over its airports

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.

Aalborg airport was forced to shut down for several hours on Wednesday evening after green lights were spotted overhead, while Billund airport also briefly closed. Three smaller airports also reported drone activity.

On Monday, Copenhagen airport temporarily closed due to a drone incursion.

Defence Minister Troels Lund Poulsen told a news conference that the "hybrid attack" was part of a "systematic operation", but said the devices had been launched locally.

A hybrid attack uses a mix of military and non-military tactics and is designed to interfere with a nation's infrastructure or institutions.

Drones pose a risk of colliding with planes, particularly during take-off or landing, but halting air traffic in and out of an airport to avoid this can cause delays and flights being redirected elsewhere.

At least three flights were diverted away from Aalborg during the incident.