Ukrainian government troops moved against pro-Russia forces in the east of the country, killing up to five of them in clashes at insurgent-held checkpoints in Slaviansk.

"During the clashes five terrorists were killed," a spokesman said, adding that a soldier was also wounded.

Russian President Vladimir Putin threatened Kiev with consequences: "If the Kiev government is using the army against its own people this is clearly a grave crime."

The operation came as Kiev resumed military operations to oust pro-Russian militants who have been occupying government buildings in numerous eastern cities.

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Ukrainian special forces take position as they launch an assault on the rebel-held town of SlavianskAFP
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A member of the Ukrainian special forces takes position at an abandoned roadblock in SlavianskAFP
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A man talking on the phone flees a checkpoint after Ukrainian special forces took position in the eastern Ukrainian city of SlavianskAFP
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A Ukrainian security force officer is deployed at a checkpoint set on fire and left by pro-Russian separatists near SlavianskReuters
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An armed member of the Ukrainian special forces sits on top of an armoured personnel carrier in Slaviansk after Ukraine's military launched an assault on the rebel-held townAFP
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Masked pro-Russia protesters stand guard near a barricade outside a regional government building in DonetskReuters
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A dog wrapped in a Russian flag sits with pro-Russia protesters outside a regional government building in DonetskReuters
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Pro-Russian protesters walk past a sign telling the West not to interfere, at the seized office of the SBU state security service in LuhanskReuters
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A Pro-Russian supporter walks past the seized offices of the SBU state security service in LuhanskReuters
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An armed pro-Russian man stands guard outside a regional government building seized by them in KramatorskReuters
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Relatives of Donetsk deputy Volodymyr Rybak carry his picture and wreaths during his funeral in the village of Horlivka, in eastern Ukraine. The Ukrainian town councillor's apparent torture and murder helped to prompt a threatened new government offensive in the east. He was mobbed by a hostile, pro-Russian crowd before he disappeared, a video of the incident showsReuters