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GRAFENWOEHR, Germany — Vladimir Putin's aggression in Ukraine and other intimidating shows of force have created a "very different kind of scenario" for NATO, according to the defense alliance's top commander in Europe.

On Monday, 28 Russian military planes including TU-95 and TU-22 strategic bombers were intercepted over the Baltic Sea near Latvia's border. On Tuesday, a Russian plane violated Estonia's airspace. Poland's defense minister later accused Putin of launching "unprecedented activity" around the Baltic Sea.

Gen. Philip Breedlove, NATO’s Supreme Allied Commander Europe, said the recent Russian flights were "of a different nature than we've seen in a while." The warplanes were intercepted by NATO in international airspace.

"For the past 19 years, we have been trying to treat Russia as a partner, trying to bring the nations of Europe back together and now what we see is a very different kind of scenario,” Breedlove told NBC News.

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Moscow's military manoeuvres this week did nothing to help ease tensions between the West and Russia over the Ukraine crisis and NATO commanders stress that it is "time to re-focus" the alliance.

In its latest move to reassure nervous allies that border Russia, NATO leaders met in Germany this week to analyze the results of Exercise Trident Lance 2014. Its training scenario dealt with the hypothetical invasion of NATO member Estonia and included everything from missile strikes to cyber attacks. It was the first NATO exercise of its kind since the end of the Cold War.

In the wake of Russia's annexation of Crimea and alleged support of Ukraine separatists, NATO is also creating a new "spearhead force." It aims to deploy more quickly than the alliance’s current rapid reaction force.

By 2016, NATO wants to establish a brigade-size force of up to 5,000 ground troops that's ready to be sent to trouble spots at short notice, with air, sea and special forces support.

"We are evolving in order to be more responsive," said Breedlove, who also heads the U.S. European Command.

The so-called Very High Readiness Joint Task Force (VJTF) will "have an adjustable response that could go as low as two days based on intelligence and warning," Breedlove said.

Held in Bavaria, Exercise Trident Lance 2014 included more than 3,700 troops from various locations across Europe and featured both computer and traditional military training events.

General Jean-Paul Palomeros, NATO Supreme Allied Commander Transformation, described the current security situation in Eastern Europe as "very complex and very volatile."

He added: "NATO has to face a lot of challenges together."

Reuters contributed to this report.