Danish police said on Tuesday that drones that shut the country's main airport on Monday appeared to have been flown by "a capable operator", adding that no suspects had been identified.
The airports in Copenhagen and Oslo, the two busiest in the Nordic region, were shut for hours after drones were observed in their airspace late on Monday, leaving tens of thousands of passengers stranded as flights were diverted.
"We have concluded that this was what we would call a capable operator," Danish police Chief Superintendent Jens Jespersen told reporters on Tuesday, referring to the drones observed in Copenhagen.
"It's an actor who has the capabilities, the will and the tools to show off in this way," Jespersen said, adding that it was too early to say if the incidents in Denmark and Norway were linked.
Copenhagen Airport was closed for four hours when two or three large drones were seen flying in its immediate vicinity, officials said, while the Oslo Airport was closed for three hours following two sightings, according to local police.
Jespersen said the drones in Denmark came from several different directions, turning their lights on and off, before eventually disappearing after several hours.

Sydney Airport flights disrupted due to air traffic controller shortage
Philippine firefighters enter charred ferry as search continues for dozens missing
Modi, Putin hold talks in New Delhi on trade, defence
More US lawmakers seek AI rules after Anthropic researchers warn of extinction
Fire in rebel-held east Congo kills 24 schoolchildren
Trump says he does not regret Iran war despite potential impact on elections
Trump touts $5,000 payout if Republicans win as Vance waits in wings
Search expands after Philippine ferry fire kills five and leaves dozens missing
