Russia has been testing their combat readiness raising fears that they may interfere:
http://www.theguardian.com/world/201...mea-separatism
http://www.theguardian.com/world/201...mea-separatism
They did invade Georgia a few years ago to under similar circumstances to maintain Russian control and influence in South Ossetia. Still, interference in Ukraine would most like end up pretty messy.
Pro-Russian demonstrations also took place in Crimea, however 10,000 Crimean Tatars took to the streets to support the interim Ukraine government and most Tatar groups have declared themselves on the side of the revolutionaries and desire closer ties with Europe.
http://en.ria.ru/russia/20140226/187...ars-Clash.html