bRussia warns of civil war if Ukraine uses force to quell eastern revolts/b
iBy Laura Smith-Spark and Victoria Butenko, CNN/i
Kiev (CNN) -- (CNN) -- Russia warned Tuesday that any use of force in Ukraine's eastern region could lead to civil war, as Kiev seeks to regain control after pro-Moscow uprisings in three cities.
Pro-Russian protesters seized government buildings in the three cities of Donetsk, Luhansk and Kharkiv on Sunday. Rebels occupying Donetsk's regional government building Monday declared a "people's republic" and called for a referendum on secession from Ukraine to be held by May 11.
Russia's Foreign Ministry said reports that the protesters are facing a crackdown by Ukrainian authorities are of particular concern.
"We are calling for the immediate cessation of any military preparations, which could lead to civil war," it said in a statement on its official website.
The ministry alleged that what it called "American experts from the private military organization Greystone," disguised as soldiers, as well as militants from the Ukrainian far-right group Right Sector, had joined Ukrainian forces preparing for the crackdown in the country's east.
Meanwhile, the U.S. Navy warship USS Donald Cook is scheduled to enter the Black Sea no later than Thursday as part of the latest U.S. military effort to demonstrate support for Eastern European allies concerned about Russia's troop buildup, two U.S. military officials said.
The ship will conduct exercises and port visits while in the Black Sea, said the officials, who spoke on condition of anonymity because a formal announcement has not been made.
The move comes ahead of an April 15 meeting among top NATO political representatives, who will discuss and potentially approve NATO recommendations for additional military measures, including shortening the response time of NATO forces in a crisis. Other options include more military exercises with member nations, including the United States, and potentially providing military advisers to Ukraine.
Secretary of State John Kerry said Tuesday that Russian forces and special agents have been behind what he called the "chaos" in eastern Ukraine in the past 24 hours. Kerry described the developments as "more than deeply disturbing" and said they amounted to what could be a "contrived pretext for military intervention just as we saw in Crimea."