The move came as Ukranian forces began mobilizing for a possible confrontation with Russia and world leaders cautioned Russia to withdraw troops it sent to the Crimea.
U.S. Secretary of State John Kerry will visit Kiev Tuesday, the State Department said.
Viktoria Siumar, deputy secretary of Security and Defense Council announced Berezovsky's firing at a news briefing, KvyvPost reported.
Siumar added Berezovsky is being investigated on suspicion on treason and "Rear Adm. Sergiy Haiduk has been appointed on his place."
Meanwhile, the Luhansk Oblast Council, which governs Ukraine's easternmost Luhansk province, said it doesn't recognize the legitimacy of Ukraine's new government, KvyvPost said.
The regional council "considers illegitimate all central executive branches of power because they were formed with violation of laws," a statement from the council said.
The council further called on the Ukrainian Parliament "to declare the Russian language a second state language in Ukraine, to take immediate measures to disarm all illegal armed groups and to cease politically motivated prosecutions of police and Berkut riot-control police units," the statement said.
Ukrainian leaders Sunday accused Russia of declaring war, and began mobilizing troops and calling up reservists.
The action came after Russian troops moved into the Crimea, ostensibly to protect Russian ethnics. Vladislav Seleznyov, spokesman for the Crimean Media Center of the Ukrainian Defense Ministry, told CNN Russian troops had blocked three bases and were demanding Ukranian soldiers surrender their arms although there had not yet been any "open confrontation."
Prime Minister Arseniy Yatseniuk urged Russia to pull back its military, calling Moscow's actions "a declaration of war to my country."
"This is a red alert. This is not a threat. This is actually a declaration of war to my country," Yatsenyuk said.
NATO Secretary General Anders Fogh Rasmussen demanded Russia stop moving troops into the Crimea, saying the deployment "violates the principles of the United Nations Charter. It threatens peace and security in Europe."
Since Russian President Vladimir Putin obtained parliamentary approval to send Russian forces to Ukraine Saturday, Russian troops have spread out in the Crimea, the Washington Post reported.
Moscow's decision to send troops to Ukraine was made after Crimea Premier Sergei Aksenov asked Russia for help deterring anti-government protesters. A large majority of residents in Crimea are ethnic Russians.
"This is actually a declaration of war to my country," Yatseniuk said. "If he wants to be the president who started the war between two neighboring and friendly countries, he is within just a few inches of his target. We are on the brink of disaster."
Hundreds of demonstrators took to the streets in Moscow Sunday to protest military intervention in Ukraine, KvyvPost reported.
"You achieved historical victory over tyranny," said writer Bernar Anri-Levi, who addressed the rally. "You are the best Europeans, it's the first time in history that people died holding EU flags. But today another force is standing in front of you, the force that is trying to destroy Ukraine. Europe has to help you to gain victory over Putin. You have to sign the association agreement tomorrow, literally tomorrow, and it will be a protection for you."
Russian media reported 265 protesters were arrested in Moscow, while 20 were arrested in St. Petersburg.
A number of foreign officials have spoken out against Russia's actions, including U.S. President Barack Obama, who conducted a 90 minute phone call with Putin Saturday night, Voice of America reported.
During the phone call, Obama expressed concern about Russia's military intervention, calling it a violation of Ukrainian sovereignty and international law.
Kerry appeared on the CBS program "Face the Nation" and called Russia's actions an "incredible act of aggression" and threatened "very serious repercussions" from the United States.
Canadian Prime Minister Stephen Harper recalled its ambassador to Moscow, the government said in a statement.
U.K. Foreign Secretary William Hague said Britain would pull out from preparatory Group of Eight talks, the BBC said.
"The sovereignty and the territorial integrity of Ukraine has been violated and this cannot be the way to conduct international affairs," Hague said. "And so in addition to calling yesterday's emergency meeting of the U.N. security council, the United Kingdom will join other G8 countries this week in suspending our cooperation under the G8 which Russia chairs."
France and the United States have also pulled out of the G8 prep meetings.
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