Estonian Defense Minister Hanno Pevkur also said the government had decided "to start consultations among the allies" under NATO's article 4, he wrote on X, after Russian jets "violated our airspace yet again."

The North Atlantic Council, NATO's principal political decision-making body, is due to convene early next week to discuss the incident in more detail, NATO spokesperson Allison Hart said Friday.

Article 4, the shortest of the NATO treaty's 14 articles, states that: "The Parties will consult together whenever, in the opinion of any of them, the territorial integrity, political independence or security of any of the Parties is threatened."

Russian officials did not immediately comment.

Russia's violation of Poland's airspace was the most serious cross-border incident into a NATO member country since the war in Ukraine began with Russia's all-out invasion in February 2022. Other alliance countries have reported similar incursions and drone crashes on their territory.

The developments have increasingly rattled European governments as US-led efforts to stop the war in Ukraine have come to nothing.

The European Union's foreign policy chief Kaja Kallas called Friday's incursion "an extremely dangerous provocation" that "further escalates tensions in the region."

"On our side, we see that we must show no weakness because weakness is something that invites Russia to do more," she said. "They are increasingly more dangerous -- not only to Ukraine, but also to all the countries around Russia."

Estonia, along with fellow Baltic states Lithuania and Latvia and neighboring Poland, are staunch supporters of Ukraine.

The Russian MIG-31 fighters entered Estonian airspace in the area of Vaindloo Island, a small island located in the Gulf of Finland in the Baltic Sea, the Estonian military said in a separate statement.

The aircraft did not have flight plans and their transponders were turned off, the statement said, nor were the aircraft in two-way radio communication with Estonian air traffic services.

Italian Air Force F-35 jets, currently deployed as part of the NATO Baltic Air Policing Mission, responded to the incursion, according to the statement.

In a post on social media, Hart described the incident as "another example of reckless Russian behavior and NATO's ability to respond."

NATO fighter jets scramble hundreds of times most years to intercept aircraft, many of them Russian warplanes in northwest Europe flying too close to the airspace of its member countries, but it's rarer for planes to cross the boundary.

Dozens of NATO jets are on round-the-clock alert across Europe to respond to incidents such as unannounced military flights or civilian planes losing communication with air traffic controllers.

Separately, Major Taavi Karotamm, spokesperson for the Estonian Defense Forces, said the Russian planes flew parallel to the Estonian border from east to west and did not head toward the capital, Tallinn.

Karotamm said the reason for the border violation is unknown, but added that it may have been to "shift the focus of NATO and its members on to defending itself, rather than bolstering Ukrainian defense."

"Russia's increasingly extensive testing of boundaries and growing aggressiveness must be met with a swift increase in political and economic pressure," Tsakhna, the foreign minister, said.

The Russian charge d'affaires was summoned and given a protest note, a ministry statement said.

Earlier Friday, the head of Britain's foreign intelligence agency said there is "absolutely no evidence" that Russia's President Vladimir Putin wants to negotiate peace in Ukraine.

Richard Moore, chief of the Secret Intelligence Service, or MI6 as it is more commonly known, said Putin was "stringing us along."

"He seeks to impose his imperial will by all means at his disposal. But he cannot succeed," Moore said. "Bluntly, Putin has bitten off more than he can chew. He thought he was going to win an easy victory. But he -- and many others -- underestimated the Ukrainians."

The war has continued unabated in the three years since Russia invaded its neighbor. Ukraine has accepted proposals for a cease-fire and a summit meeting, but Moscow has demurred.

President Trump said Thursday during a state visit to the United Kingdom that Putin " has really let me down " in peace efforts.

Moore was speaking at the British consulate in Istanbul after five years as head of MI6. He leaves the post at the end of September. The agency will then get its first female chief.

Moore said the invasion had strengthened Ukrainian national identity and accelerated its westward trajectory, as well as pushing Sweden and Finland to join NATO.

"Putin has sought to convince the world that Russian victory is inevitable. But he lies. He lies to the world. He lies to his people. Perhaps he even lies to himself," Moore told a news conference.

Estonia says 3 Russian fighter jets entered its airspace in 'brazen' incursion - The Boston Globe