In a statement published Thursday, the Russian Foreign Ministry lashed out at Anders Fogh Rasmussen, accusing him of turning NATO into an ``elite club'' that employed “double tandards'' in international politics.

In a speech in Paris on Tuesday, Rasmussen demanded that Russia pull back the tens of thousands of troops NATO says it has amassed on Ukraine's border.

The alliance says Moscow is using the troops to maintain pressure on the Kiev government, and preparing for possible invasion.

In March, Russian troops took control of Ukraine's Crimean Peninsula, whose inhabitants then voted in a referendum to secede and join Russia.

NATO also warned Russia that any further intervention in Ukraine would be a “historic mistake”.

“I urge Russia to step back and not escalate the situation in east Ukraine,” said Rasmussen.

Hundreds of pro-Russia demonstrators seized and barricaded themselves inside government buildings in the east Ukrainian cities of Kharkiv, Donetsk and Luhansk on Sunday night, chanting “Russia! Russia!” and calling for “peacekeepers” to be sent in from across the frontier.

Demonstrators are demanding a referendum to facilitate the secession of eastern provinces from Ukraine to join Russia, in a similar vein to what recently took place in Crimea.

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