Kastrup airport in Copenhagen was forced to shut for several hours from around 20:30 (18:30 GMT) on Monday following the sighting of a number of drones. The drone incursion that stopped flights at Copenhagen airport on Monday night was "the most severe attack on Danish infrastructure so far", Denmark's Prime Minister Mette Frederiksen said. Around 20,000 passengers were impacted by the closure of Copenhagen airport, which resumed operations after midnight local time. A number of large drones which had come from different directions "quite a long way away" had been observed at Copenhagen airport, said police Inspector Jens Jespersen. In a post on social media Ukrainian President Volodymyr Zelensky referenced "Russia's violation" of Nato airspace in Copenhagen on 22 September.