Danish Defense Minister Troels Lund Poulsen (L) and Danish Justice Minister Peter Hummelgaard (R) told a news conference in Copenhagen that recent disruption to air travel caused by drones flying in and around airports, including several incidents on Wednesday night, bore all the hallmarks of a hybrid attack. Photo by Emil Helms/EPA

Sept. 25 (UPI) -- Authorities in Denmark said Thursday that a slew of incidents involving unidentified drones in the Scandinavian country's airspace in recent days that have shuttered airports were "hybrid attacks," but stressed they did not believe Russia was behind them.

Following fresh sightings Wednesday over the Skrydstrup air base and the closure of Aalborg Airport for the second time in three days, as well as over the southern cities of Esbjerg and Sonderborg, Defense Minister Troels Lund Poulson told a news briefing that the pattern of attacks pointed to a "professional actor."

He said the systematic nature of the operation made it what he defined as "a hybrid attack using different types of drones," but that the location they had been launched from was somewhere local.

Poulson said that while there was no evidence of any direct link to Russia, Denmark was not without options with response avenues via NATO, including invoking Article 4 under which any member country can formally put matters in front of the alliance's North Atlantic Council.