Estonia summoned a Russian diplomat to protest after three Russian fighter aircraft entered its airspace without permission Friday and stayed there for 12 minutes, the Foreign Ministry said, just over a week after NATO planes downed Russian drones over Poland and heightened fears that the war in Ukraine could spill over.

Foreign Minister Margus Tsakhna said that Russia violated Estonian airspace four times this year “but today’s incursion, involving three fighter aircraft entering our airspace, is unprecedentedly brazen.”

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 U.S.-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.”

Estonia, along with other Baltic states Lithuania and Latvia, are seen as being among the most likely targets if Russia one day decides to risk an attack on NATO. Neighboring Poland, though much larger, also feels vulnerable. All four countries 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 fighter jets, currently deployed as part of the NATO Baltic Air Policing Mission, responded to the incident, according to the statement.

In a post on social media, NATO spokesperson Allison 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, Maj. Taavi Karotamm, spokesperson for Estonian Defense Forces, told The Associated Press the Russian planes flew parallel to the Estonian border from east to west and did not head toward the capital, Tallinn.

“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 ceasefire and a summit meeting, but Moscow has demurred.

U.S. President Donald 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.

He said that Putin was “mortgaging his country’s future for his own personal legacy and a distorted version of history” and the war was “accelerating this decline.”

Analysts say Putin believes he can outlast the political commitment of Ukraine’s Western partners and win a protracted war of attrition by wearing down Ukraine’s smaller army with sheer weight of numbers.

Ukraine, meanwhile, is racing to expand its defense cooperation with other countries and secure billions of dollars of investment in its domestic weapons industry.

The spy chief was speaking as MI6 unveiled a dark web portal to allow potential intelligence providers to contact the service. Dubbed “ Silent Courier,” the secure messaging platform aims to recruit new spies for the U.K., including in Russia.

“To those men and women in Russia who have truths to share and the courage to share them, I invite you to contact MI6,” Moore said.

Not just Russians but “anyone, anywhere in the world” would be able to use the portal to offer sensitive information on terrorism or “hostile intelligence activity,” he said.

AP European security correspondent Emma Burrows in Vilnius, Lithuania, and AP writer Lorne Cook in Brussels contributed.

Follow AP’s coverage of the war in Ukraine at https://apnews.com/hub/russia-ukraine