Even the Party of Regions, Mr. Yanukovych’s former governing party, declined to support the pro-Russian protest movement and its demands for a referendum on the status of the east, a move that could pave the way for secession, as happened in Crimea, which Russia annexed last month. Instead, local party barons held a news conference to denounce the seizure of official buildings and to call on protesters to quickly end their occupation and accept that Donetsk is part of Ukraine.