Speaking at a press conference on Monday, Yatsenyuk said, "It is the personal responsibility of Russia and the Russian leadership for everything that is happening in Crimea."
The prime minister appealed to the Russian government to withdraw its support for the Crimean parliament's proposed referendum to determine whether to remain part of Ukraine or secede and join the Russian Federation.
"The Russian Federation must immediately cancel the referendum in the Autonomous Republic of Crimea (which is an integral part of Ukraine), and any talk that this referendum is being held by the Crimean authorities is false. There are no legitimate Crimean authorities: there is a group of criminals who seized power in Crimea in an unconstitutional manner under the guise of 18,000 Russian troops."
The Crimean parliament initially scheduled the referendum for March 16, although there are reports it has been rescheduled to March 30.
Yatsenyuk added that despite Ukraine requesting the deployment of international observers, the Russian military has barred them from entering Crimea.
[Interfax Ukraine News Agency]