Ukraine’s acting President Aleksandr Turchynov said the armed forces were launching a “full-scale anti-terrorist operation” to quell pro-Russian protests in the rebellious east of the country.

In a televised address to the nation on Sunday afternoon Mr. Turchynov said the authorities will not allow the “repetition of the Crimean scenario” in eastern Ukraine. He offered immunity from prosecution to protesters who would lay down their arms by Monday morning.

Apparently unsure of the loyalty of the military, the Ukrainian Interior Ministry announced the deployment in eastern Ukraine of the newly formed National Guard composed of far-right “self-defence forces” from western Ukraine who spearheaded violent pro-Western protests in the capital Kiev two months ago.

Russia has called for an emergency meeting of the U.N. Security Council to discuss the crisis in eastern Ukraine.

The Russian Foreign Ministry denounced the Ukrainian authorities’ “criminal” decision to use the army to crush popular protests and demanded that Kiev halt a “war against its own people.”

Earlier on Sunday acting Interior Minister Arsen Avakov announced that the anti-terror operation had already begun. He said an officer with the security service SBU had been killed and five others had been wounded in a gun battle near the eastern industrial city of Slaviansk. He said there were “unidentifiable number” of casualties among the protesters as well.

However, a local lawmaker who witnessed the incident said pro-Russian protesters were not involved. According to him, it was a provocation staged by unidentified people who had opened fire on security forces from a car with the license plates of western Ukraine.

As of late Sunday evening, the government forces had not launched an offensive.

Pro-Russian protesters have seized government buildings in at least eight cities in Ukraine’s southeast to back their demand for a referendum on greater autonomy from Kiev. On Saturday and Sunday the cities of Slaviansk, Kramatorsk, Mariupol, Yenakiyevo, Gorlovka and Druzhkovka joined the week-long anti-Kiev revolt in Donetsk and Lugansk.

On Sunday, supporters and opponents of Ukraine’s pro-Western government clashed in southeastern cities of Kharkiv and Odessa.

Kiev decided to crush pro-Russian protests under pressure from CIA Director John Brennan who visited Ukraine on Saturday, Russia’s Interfax news agency reported on Sunday quoting a source in the Ukrainian Parliament.

As tension built up in eastern Ukraine, U.S. and Russian top diplomats had an angry exchange of warnings and threats over the telephone on Saturday.

U.S. Secretary of State John Kerry called his Russian counterpart Sergei Lavrov to voice “strong concerns” about fresh attacks by armed militants in eastern Ukraine and threaten “additional consequences” if Russia failed to “de-escalate” the situation in Ukraine.

According to the State Department, Mr Kerry said the protests in eastern Ukraine “were orchestrated and synchronized.”

Mr Lavrov, for his part, warned Mr Kerry that “if Kiev carries out its threats to use force against people driven to despair in the southeast, prospects for further cooperation on the Ukrainian issue, including a planned four-party meeting in Geneva, will be derailed,” the Russian Foreign Ministry said.

Western leaders have openly backed Kiev’s crackdown on pro-Russian protesters.

E.U. foreign policy chief Catherine Ashton said in a statement on Sunday that the E.U. “commends the Ukrainian authorities for pursuing their law and order operations in a measured way.”

Sweden’s Foreign Minister Carl Bildt said on Twitter that on a visit to Ukraine in Sunday he “expressed support for efforts of Ukraine government to protect democracy.”

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