Kremlin. warned it will act to protect eastern Ukraine's Russian-speakers if they come under attack. operation" to re-assert Kiev's control in Slaviansk. flying over the town's police headquarters where militants were holed up. windows," Avakov wrote on his Facebook page. any one had been hurt. into Slaviansk, but there was no independent confirmation of this. Sunday business. Ukraine that began when the Moscow-backed president was pushed out, and Moscow annexed Ukraine's Crimean peninsula. to a Russian military incursion, though Moscow has strenuously denied any such intention. further military intervention," said Laura Lucas Magnuson, spokeswoman for the White House National Security Council. U.S. Vice President Joe Biden will travel to Kiev on April 22, becoming the most senior U.S.