Russia warned Ukraine’s authorities that the use of force to suppress protests in the Russian-speaking eastern regions could trigger civil war.

Moscow voiced particular concern over the deployment in the east of ‘about 150’ American mercenaries from the Greystone private army disguised as Ukrainian military personnel.

Kiev has reportedly sent army and national guard forces to eastern Ukraine to quell pro-Russian protests. On Monday protesters in Donetsk proclaimed the region’s independence from Ukraine and called for a referendum to join Russia.

“We are calling for the immediate cessation of any military preparations, which are fraught with unleashing civil war,” the Russian Foreign Ministry said in a statement on Tuesday.

Late on Monday Ukrainian security forces evicted pro-Russian protesters from the local government headquarters in Kharkiv and the Ukrainian security service building in Donetsk which had been captured on Sunday, the government in Kiev announced. However, protesters continued to occupy the security services headquarters in Lugansk. They have armed themselves with firearms seized from the arsenal in the building.

Ukraine’s Interior Minister Avakov said on Tuesday about 70 ‘separatists’ had been detained in Kharkiv.

“An anti-terrorist operation has been launched. The city centre is blocked along with metro stations. Do not worry. Once we finish, we will open them again,” he wrote on his Facebook page.

Russia’s Foreign Minister Sergei Lavrov called U.S. Secretary of State John Kerry and German Foreign Minister Frank-Walter Steinmeier to press the need for a ‘deep and transparent constitutional reform involving all political forces and regions’ that would make Ukraine a federative non-bloc state.

Mr. Lavrov said Moscow was ready to take part in four-party talks over the crisis with Ukraine, the European Union (EU) and the U.S. proposed by Mr. Kerry. However, he said protesters from Ukraine’s eastern regions should also take part in the talks and their agenda should include a constitutional reform in Ukraine.

“No multilateral talks will be effective if they ignore the legitimate interests of Ukraine’s south and east and their indignation over the way Kiev has been treating them,” Mr. Lavrov told a press conference in Moscow on Tuesday.

The Russian Minister angrily rejected U.S. claims that the protests in Ukraine’s eastern regions were ‘a carefully orchestrated campaign with Russian support.’

To say this means ‘laying their own blame at our door,’ Mr. Lavrov retorted, recalling that the U.S. had spent billions of dollars financing pro-Western protests in Kiev, which led to the fall of President Viktor Yanukovych in February.

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