Crowds of pro-Russia protesters have stormed government buildings in the eastern Ukrainian cities of Donetsk and Luhansk, waving Russian flags and calling for regional referendums on independence.
In Donetsk Sunday, a large group of people pushed into the regional government building, barricaded the doors, and hung a Russian flag from a window. Hundreds of protesters thronged in the city square below, cheering when those inside the building tossed a Ukrainan flag out the window.
In nearby Luhansk, protesters also broke into a government building. Outside, police in riot gear clashed with masked protesters, who lobbed firecrackers in the air and kicked and yanked at the security forces' metal shields.
A spokesman for Ukraine's acting president, Oleksandr Turchnyov, said he canceled a trip to Lithuania Sunday and called an emergency meeting of security chiefs in Kyiv because of the protests.
Ukraine's interior minister, Arsen Avakov, posted a message on social media accusing Russia's President Vladimir Putin and former Ukrainian president Viktor Yanukovych of instigating and financing the latest protests.
Last month, Russia annexed the Crimean peninsula from Ukraine, after a regional referendum resulting in an overwhelming vote to declare independence from Ukraine and an intention to join the Russian Federation.
On Friday, British Foreign Minister William Hague said Europe should continue its "strong and united" response to Russia's escalation of the Ukrainian crisis. He said there has only been a "token withdrawal" of the troops massed near the Ukrainian border, whose presence has raised fears of a Russian invasion.
Western nations already have adopted sanctions against Russia because of its annexation of the Crimean peninsula, a move rejected by the United States and its allies.
Russia moved into the peninsula last month following the ouster of Ukraine's Moscow-backed president Yanukovych. He fled after weeks of opposition protests calling for him to step down.