Denmark was forced to close its biggest airport on Monday night due to drone sightings. Danish police told reporters on Tuesday morning that they were likely flown by a “capable actor” who wanted to “show off” and possibly practicing.

Denmark’s Copenhagen Airport was forced to close on Monday evening after police said two or three large drones had been seen flying in the area.

In a statement, the airport warned of ongoing delays and cancellations, and urged passengers to check the status of their flight with their airlines.

“Copenhagen Airport is currently closed for takeoff and landing, as 2-3 large drones have been seen flying in the area. The time horizon is currently unknown,” the police said in a short post on X.

In a press conference in Copenhagen, the police provided an update on the situation regarding the drones at Copenhagen Airport. Police said there was nothing to indicate that the drones were intended to cause harm.

Asked by reporters if the drones were of Russian origin, a police official said he could not confirm or deny this. “Which capable actor, I do not know,” the official said.

Local media showed a significant police presence in the vicinity of the airport.

Operations at Copenhagen airport resumed, though delays and cancellations continued, the airport’s website said on Tuesday. “Copenhagen Airport has reopened after being closed due to drone activity. However, there will be delays and some cancelled departures. Passengers are advised to check with their airline for further information.”

Investigators are looking at how the drones reached the airport – whether it was by land or if the drones were launched from ships.

Investigations will also show if the drones are part of a hybrid attack. Russia has consistently denied responsibility for any hybrid attack in Europe, calling the accusation “baseless.”

In a social media post later, Ukrainian president Volodymyr Zelenskyy referenced “Russia’s violations of the airspace of NATO member states, including on September 22 in Copenhagen,” but did not indicate a source for the information. “If there is no resolute response from the allies – both states and institutions – to aggressive provocations, Russia will continue them,” the Ukrainian president added on X.

European Commission President Ursula von der Leyen highlighted the security risks following drone activity at Copenhagen Airport, calling it part of a broader border threat. She stressed on social media that the protection of critical infrastructure is vital, as authorities work to determine the facts.

NATO Secretary General Mark Rutte commented on the drone incident over Denmark that occurred on the evening of September 22. He said that the Alliance would provide support to Denmark and involve allies in the investigation and appropriate actions.

“I spoke with the Danish Prime Minister, and of course, also Denmark is still assessing what exactly happened and whether they can find out more. And of course, we will help wherever we can, and all our Allies will be involved in that, as is always the case when these serious incidents happen,” the NATO Secretary General noted.

Rutte also remarked that: if needed, NATO will not hesitate to respond.