SIMFEROPOL, UKRAINE - Witnesses and Western analysts say thousands of Russian military personnel have crossed into Crimea since last week, setting off a groundswell of Western condemnation against Russian President Vladimir Putin, and warnings of stiff penalties if Moscow fails to withdraw.
Russian and pro-Russian forces in Crimea continue to consolidate their hold of the region, reinforcing barricades around Ukrainian military bases and scuttling a ship to block the Ukrainian navy.
The military actions come as a political showdown looms over the future of the Ukrainian autonomous region.
The local pro-Russian parliament called for a referendum in just over a week on whether Crimea should break with Ukraine and join the Russian Federation.  Lawmakers have already unanimously approved the measure.
Ukrainian, European and U.S. leaders have all denounced any attempt at secession, saying such a vote would be illegal under Ukrainian and international law.
President Obama spoke at length by telephone with Russian President Vladimir Putin late Thursday. Obama argued that there is still time to resolve the dispute diplomatically. In a statement afterward, Putin said Russia couldn't ignore Crimea's calls for help and is acting within international law.
Crimea has an ethnic Russian majority and long historical ties to Moscow.  With Russian soldiers and pro-Russian vigilantes roaming the streets, fear is rising for those who want to stay within Ukraine.