This is a move to restrict Ukraine's move to the west or to unaligned status which Vladimir Putin does not want.
Watch this one; it can get ugly pretty quickly.
Ukraine’s east is heavily Russified and is called the “novorossiya.” Yanukovych’s political base is with voters east of the Dnieper and they all favor closer ties to Russia. And the Party Of Regions has close ties to the Russian “party of power,” United Russia. For Moscow, given Western threats against a friendly country, there are no downsides and are plenty of upsides.
Yanukovich, the Russian SOB is paranoid, however his continuing Stalinist thuggery may result in an Orange Winter!