Ukrainian authorities are threatening to use force against pro-Russian separatists who've taken control of government buildings in several cities in the east.
They've given the protestors two days to get out.
In the city of Luhansk, pro-Russian demonstrators seized the government security building and raised a barricade out front.
Hundreds camped out, chanting the name of Russian President Vladimir Putin.
The Ukrainian government says Russia is fostering the unrest in an attempt to expand its influence over eastern Ukraine.
Meanwhile, NATO has released pictures of the tens of thousands of Russian troops amassed on the Ukraine border.
Russia is also threatening to make Ukraine pay for its natural gas shipments in advance, which could cripple its weak economy.