NATO on Tuesday accused Moscow of an escalating campaign of airspace violations over eastern and northern alliance member states.

"Russia should be in no doubt: NATO and Allies will employ, in accordance with international law, all necessary military and non-military tools to defend ourselves and deter all threats from all directions," NATO Secretary General Mark Rutte told reporters in Brussels.

The 32-member alliance was holding urgent talks after a Russian jet was spotted over Estonia last week, which came shortly after Russian drones were shot down over Poland and spotted over Romania.

Drones spotted over Copenhagen, Oslo airports

The statement came after large drones were seen circling above the airport in the Danish capital on Monday. 

Copenhagen airport was shut for several hours, as was the airport in Oslo, Norway, where drones were also seen flying overheard.

Danish Prime Minister Mette Frederiksen called the incident "the most serious attack on Danish critical infrastructure."

While authorities said they had not yet identified a culprit, the scale of the attack suggested a "capable actor" and Frederiksen said Russian involvement "could not be ruled out."

Ukraine's Volodymyr Zelenskyy condemned the incident on X as a violation of Danish airspace by the Kremlin.

European Commission President Ursula von der Leyen said that the drones in the Danish capital were "pattern of persistent contestation at our borders."

"Our critical infrastructure is at risk," she wrote on X, adding that all the facts had yet to be established.

Dmitry Peskov, spokesman for Russian President Vladimir Putin, called the insinuations that Moscow was responsible "unfounded."

Norway also accuses Russia of violating airspace

Meanwhile, Norwegian Prime Minister Jonas Gahr Store said: "Russia has violated Norwegian airspace on three occasions this spring and summer."

He pointed to several times Russian fighter jets were spotted on Norway's side of their shared border.

"We cannot determine whether this was done intentionally or due to navigation errors. Regardless of the cause, this is not acceptable," he said, without confirming suspicions that the Kremlin was also behind Monday's disturbance in Oslo.

NATO chief Rutte said it was "too early to say" whether the drone flights over Denmark were connected to Russia's recent violations of NATO airspace.

Edited by: Dmytro Hubenko