Poland shot down drones that entered its airspace on Wednesday, the first time a member of NATO is known to have fired shots during Russia's war in Ukraine.
The violation of Poland's airspace by Russian drones was "absolutely reckless", NATO Secretary General Mark Rutte said on Wednesday, adding that a full assessment of the incident had not yet been made.
"Whether it was intentionally or not, it is absolutely reckless, it is absolutely dangerous. But the full assessment is ongoing," Rutte said.
"To Putin, my message is clear. Stop the war in Ukraine. Stop violating allied airspace. And know that we stand ready, that we are vigilant, and that we will defend every inch of NATO territory."
Poland said 19 objects had entered its airspace during a large Russian air attack on Ukraine, and that it had shot down those that posed a threat.
Prime Minister Donald Tusk said he had activated article four of NATO's treaty, under which alliance members can demand consultations with their allies.
"We are dealing with a large-scale provocation," said Tusk.
"We are ready to repel such provocations. The situation is serious, and no one doubts that we must prepare for various scenarios."
Russia's RIA state news agency quoted a Russian diplomat as calling the accusations of an incursion "groundless" and saying Poland had not given any evidence that the drones shot down were of Russian origin.
Poles warned to stay home
Several European officials described the incursion as intentional and a sign of Russian escalation.
"The fact that these drones, which posed a security threat, were shot down changes the political situation," said Tusk.
The Operational Command of the Polish Armed Forces urged residents to stay at home, with three eastern regions at particular risk.
"This is an act of aggression that posed a real threat to the safety of our citizens," it said.
Chopin Airport in Warsaw, the country's largest, closed its airspace for several hours before reopening, adding there would be disruptions and delays throughout the day.
Putin 'testing' the West
Russian drones and missiles have entered the airspace of NATO members, including Poland, several times during Russia's three-and-a-half-year war, but a NATO country has never attempted to shoot them down.
A cornerstone of the Western military alliance is the principle that an attack on any member is deemed an attack on all.
Ukraine's foreign minister Andrii Sybiha said the violations of Poland's airspace showed Russian President Vladimir Putin was expanding his war and testing the West.
"The longer he faces no strength in response, the more aggressive he gets," Sybiha said on X. "A weak response now will provoke Russia even more — and then Russian missiles and drones will fly even further into Europe."
The incident could feed into deliberations on tightening sanctions on Moscow. European countries are hoping to persuade US President Donald Trump to join them in imposing sanctions after sporadic peace talks on ending the war proved fruitless.
Countries bordering on Ukraine have reported occasional Russian missiles or drones entering their airspace in the past during the war, but not on such a large scale, and they are not known to have shot them down. Two people were killed in Poland in 2022 by a Ukrainian air defence missile that went astray.
'Intentional incursion'
Early indications suggested the entry of Russian drones into European airspace was intentional, not accidental, the EU's top diplomat Kaja Kallas said on Wednesday.
"Russia's war is escalating, not ending. We must raise the cost on Moscow, strengthen support for Ukraine, and invest in Europe's defence," Kallas said. "The EU plays a major role and we will support initiatives like the Eastern Border Shield defence line," Kallas wrote in a post on X.
US Secretary of State Marco Rubio had been briefed, CNN reporter Kaitlan Collins said on Tuesday. The State Department did not immediately respond to a request for comment.
'Extremely dangerous precedent'
Ukrainian President Volodymyr Zelenskyy said Russia used 415 drones and 40 missiles in attacks on Ukraine overnight, adding that at least eight Iranian-made shahed drones had been aimed towards Poland.
"An extremely dangerous precedent for Europe," he said. "A strong response is needed — and it can only be a joint response by all partners: Ukraine, Poland, all Europeans, the United States."
Russia has long said it has no intention of stoking a war with NATO, and that Western European countries suggesting it is a threat are trying to worsen relations.
President of the European Commission Ursula von der Leyen called for more sanctions on Russia, and said the EU was preparing sanctions on 'shadow fleet' tankers that transport its oil and third countries that buy it.
Czech Foreign Minister Jan Lipavsky called for NATO to strengthen air defences on its frontline.
Trump, who warmly welcomed Putin in Alaska at a summit in August, said over the weekend he was ready to move to a second phase of sanctioning Russia after months of talks about a peace deal.
It was his strongest indication yet that he may escalate pressure on Moscow or its oil buyers in response to the war in Ukraine.
The European Union's top sanctions official has been in Washington this week to discuss coordinated sanctions. If such are adopted, it would be the first time the United States and Europe had taken coordinated steps against Russia since Trump returned to office in January promising to end the war in 24 hours.
