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Eastern European NATO countries are on edge after Wagner Group leader Yevgeny Prigozhin's relocation to Belarus.

"This is really serious and very concerning, and we have to make very strong decisions. It requires a very, very tough answer of NATO," Polish President Andrzej Duda said of the Prigozhin move, according to a report from Reuters Tuesday.

Duda was just one of several NATO leaders who were sounding the alarm on the Wagner leader's supposed deal with the Kremlin, causing some leaders to promise increased military security on NATO's eastern flank to deter potential conflict should Wagner fighters follow Prigozhin to Belarus.

"If Wagner deploys its serial killers in Belarus, all neighboring countries face even bigger danger of instability," Lithuanian President Gitanas Nauseda said.

NATO Secretary General Jens Stoltenberg told reporters Tuesday that the alliance is unified and ready to defend NATO territory, warning more measures to beef up security could be coming.

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NATO FINLAND

An empty flagpole stands between the national flags of France and Estonia outside NATO headquarters in Brussels, Monday, April 3, 2023.  (AP Photo/Virginia Mayo)

"We have sent a clear message to Moscow and Minsk that NATO is there to protect every ally, every inch of NATO territory," Stoltenberg said. "We have already increased our military presence in the eastern part of the alliance and we will make further decisions to further strengthen our collective defence with more high-readiness forces and more capabilities at the upcoming summit."

Stoltenberg also made clear that members of the alliance will still support the Ukrainian war effort, something he said was even more important amid the latest developments.

"At the same time we must not underestimate Russia," Stoltenberg said. "So it's even more important that we continue to provide Ukraine with our support."

Rebekah Koffler, an author and former DIA intelligence officer, told Fox News Digital that Prigozhin's move could be part of a wider strategy by Russian President Vladimir Putin to spread Ukrainian defenses thin.

"It is a strategic move to beef up Russian force posture and open a second front for Western Ukraine war," author and former DIA intelligence officer Rebekah Koffler said. Koffler said her intelligence analysis has her leaning to believe, "the revolt was not authentic."

"My intel analysis suggests the coup attempt was false flag operation," Koffler told Fox News Digital. "It is a strategic move to beef up Russian force posture and open a second front for Western Ukraine war."

Koffler's comments come as Belarusian President Alexander Lukashenko confirmed Tuesday that Prigozhin had landed in his country after staging a rebellion in Russia over the weekend. The Wagner Group leader is reportedly in Belarus as part of a deal struck with the Kremlin to go into exile there in exchange for not facing prosecution, but his presence in the country has bordering NATO countries on edge.

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Prigozhin speaks in video address

Yevgeny Prigozhin, the owner of the Wagner Group military company, records his video addresses in Rostov-on-Don, Russia. (Prigozhin Press Service via AP)

"We are closely monitoring the situation and are fully prepared to react should the situation require," a Lithuanian official told Fox News Digital regarding Prigozhin's move to Belarus.

According to Koffler, countries such as Poland and Lithuania, which border Belarus to the west and north respectively, are right to view the move with suspicion, and are likely already discussing ways to beef up security.

"Poland and Lithuania almost certainly understand what has just taken place, in terms of Putin’s moving the chess pieces, and will likely be pressuring NATO for assistance in increasing their security measures and augmenting the alliance’s strategic reserves in the region," Koffler said.

Prigozhin's arrival in Belarus comes a day after he gave a speech explaining his rationale for the brief mutiny, explaining that the take-over of Russian towns and short-lived march on Moscow were an attempt to demonstrate the value of his fighters. The Wagner Group leader did not acknowledge any deal with Putin to end the uprising, instead saying that he stood down in an attempt to prevent any Russian bloodshed.

Wagner Group chief Yevgeny Prigozhin leaves Rustov in an SUV after his armed rebellion against the Russian military was called off

Wagner mercenary chief Yevgeny Prigozhin. (REUTERS/Alexander Ermochenko)

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However, Koffler said that "Prigozhin cannot be trusted any more than Putin," arguing the Wagner Group leader is only honest about his "work on behalf of Mother Russia." 

"Mother Russia is now Putin," Koffler said in response to the speech.

With Prigozhin now in Belarus, Koffler believes a much larger plan will be put in motion.

Lukashenko sabotague

Belarusian President Alexander Lukashenko, second left, speaks during his meeting with military top officials at the Obuz-Lesnovsky training ground, Belarus, Friday, Jan. 6, 2023. After Russia invaded Ukraine, guerrillas from Belarus began carrying out acts of sabotage on their country's railways, including blowing up track equipment to paralyse the rails that Russian forces used to get troops and weapons into Ukraine. Belarusian Defense Minister Viktor Khrenin is on right, and the State Secretary of the Security Council Alexander Volfovich is in centre. (Andrei Stasevich/BelTA Pool Photo via AP) (Andrei Stasevich/BelTA Pool Photo via AP)

"Putin is expanding the battlefield to stretch Ukrainian resources thin amidst Kiev’s counter-offensive," she said. "Putin also aims to hold at risk NATO’s eastern flank - it is why he recently gifted tactical nuclear weapons to Lukashenko."

The continued hostilities in Ukraine are creating a "permanent simmering crisis in Europe" that will come with "unpredictable consequences," Koffler noted, citing the fact that "nuclear weapons play a very prominent role in Russian military science and war-fighting doctrine."

Putin Lukashenko

Russian President Vladimir Putin (R) embraces his Belarussian counterpart Alexander Lukashenko during a meeting in Moscow, Russia December 29, 2018. Kirill Kudryavtsev/Pool via REUTERS (Kirill Kudryavtsev/Pool via REUTERS)

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Koffler added that the standoff has created a "strategic standoff unseen since the Cold War and the Cuban Missile Crisis," tensions she argued U.S. leadership could do more to ease.

"The fact that there have been no attempts, whatsoever, taken by Moscow, Kiev, Washington, or Brussels to de-escalate this crisis is a serious cause for concern," Koffler said. "As the Commander-in-Chief and the leader of the free world, President Biden has the opportunity to step in, exert U.S. influence and ensure stability."