Unidentified drones have been spotted flying over Aalborg Airport in northern Denmark, as well as three other smaller airports within the country. The authorities have yet to determine who is responsible for these incidents.

Defense Minister Troels Lund Poulsen suggested at a press briefing on Thursday morning (Thursday afternoon AEST) that a “professional actor” might be responsible for these “systematic” drone flights, though he didn’t provide further specifics.

Authorities said there was no danger to the public.

The purpose of these drone flyovers, according to Danish Minister of Justice Peter Hummelgaard, was to inspire fear and division. On Thursday, he added that the country is considering new measures to counter drones, including potential legislation that would enable infrastructure owners to shoot them down.

Drone sightings at Aalborg Airport, which also accommodates a military base, led to the suspension of flights for several hours. The drones were first noticed shortly before 10 pm on Wednesday and were last seen just before 1 am on Thursday (between 6 am and 9 am Thursday AEST).

Airport activities were also disrupted at Esbjerg, Sønderborg, and Skrydstrup. Skrydstrup is particularly significant as it hosts some of the Danish military’s fighter jets.

The drones, flying with their lights on around the airports, prompted authorities to decide against attempts to shoot them down, according to police. Other details have not yet been provided.

The Copenhagen drones grounded flights in the Danish capital for hours on Monday night, prompting concerns that Russia could be behind the flyover above Scandinavia’s largest airport.

It was not immediately clear whether the Copenhagen flyover was related to the incidents later in the week.