Major airports in two European countries have been forced to shut for hours due to unauthorised drones flying through their airspace.

Late Monday night, unidentified drones led to the closure of airspace over Copenhagen Airport, raising alarm regarding possible Russian involvement at Scandinavia’s busiest airport.

According to a spokesperson, the aircraft were still in the area three hours later.

The airport reopened shortly after midnight but travellers to and from the Danish capital were warned of lingering delays more than 13 hours later.

Though the entity responsible for the flyover remains unknown, both Denmark’s prime minister and NATO’s chief expressed that Russian involvement could not be dismissed.

Danish Prime Minister Mette Frederiksen called it “the most serious attack on Danish critical infrastructure to date”.

NATO’s Secretary-General, Mark Rutte, mentioned that drawing conclusions about Russia’s participation was “premature,” while Dmitry Peskov, a Kremlin spokesperson, dismissed claims of Moscow’s involvement.

Peskov elaborated in a Tuesday briefing with reporters, stating, “We frequently encounter baseless allegations, and a responsible party should refrain from making such unfounded claims repeatedly.”

Oslo Airport was also shut down due to a drone sighting.

Police in the Norwegian capital said they had arrested two foreign nationals for flying drones over a restricted area. 

There was no indication that the incident was connected to the events at the airport or in Copenhagen.

Norwegian media reported the drones were flown over the Akershus Fortress, a mediaeval castle that is sometimes used for government events.

Authorities in Copenhagen reported that the drones approached from various directions, intermittently turning their lights on and off before eventually disappearing after a few hours.

“We have concluded that this was what we would call a capable operator,” Danish police Chief Superintendent Jens Jespersen told reporters.

“It’s an actor who has the capabilities, the will and the tools to show off in this way,” he added.

Jespersen said no suspects had been identified yet.

The incidents come as Europe remains on high alert after a series of Russian incursions into NATO airspace in recent weeks.

Two weeks earlier, NATO had shot down several Kremlin-linked drones that infiltrated Polish airspace, and more recently intercepted three Russian jets over Estonian airspace during the weekend.

In an emergency meeting of the United Nations Security Council in New York, British Foreign Secretary Yvette Cooper said Moscow was risking “a direct armed confrontation between NATO and Russia” with its violations.

“Our alliance is defensive, but be under no illusion … if we need to confront planes that are operating in NATO airspace without permission, then we will do so,” she said.

New US ambassador to the UN Michael Waltz added that the United States and its allies “will defend every inch of NATO territory”.

Addressing the Russian delegation directly, Polish Deputy Prime Minister Radosław Sikorski said: “We know you don’t care for international law and you are incapable of living in peace with your neighbours”.

“Your insane nationalism contains a lust for domination that will not cease until you realise that the age of empires is over and that your empire will not be rebuilt…

“If another missile or aircraft enters our space without permission – deliberately or ‘by mistake’ – and gets shot down, and the wreckage falls on NATO territory, please don’t come here to whine about it. You have been warned.”

Jespersen said authorities had not been able to rule out the possibility of the drones over Copenhagen Airport being part of a Russian hybrid attack.

Investigators are looking at how the drones reached the airport – whether it was by land or possibly on boats coming through the strategic straits into the Baltic Sea.

– with Associated Press, CNN