At least nine people were killed Tuesday as Ukrainian police and protesters fought near the parliament building in Kyiv.
Police officials in the Ukrainian capital were quoted as saying that seven civilians had died in the violence, some from gunshot wounds, along with two police officers apparently killed by gunfire.
The heavy fighting broke out as police tried to block demonstrators marching on the parliament building in the Ukrainian capital.
Earlier Tuesday, Ukraine's interior ministry and state security agency said in a joint statement that they would be "forced to introduce order through all legal means" if unrest did not end by 6 p.m., local time (4 p.m. UTC).
Opposition leader Vitaly Klitschko urged women and children to leave the Maidan protest camp in case riot police stormed it.
U.S.-funded Radio Free Europe/Radio Liberty broadcast hours of video live from the scene, showing many of the clashes in detail.
Anti-government protests in Ukraine have been building for weeks, with activists calling for the ouster of President Viktor Yanukovych after he backed away from a trade deal with the European Union in favor of closer ties with Russia.
European Union foreign policy chief Catherine Ashton said Tuesday she was "deeply worried" by the "grave new escalation" in Kyiv and condemned "all use of violence, including against public or party buildings."
Ashton urged Ukraine's political leaders "to address the root causes of the crisis."
In Moscow, the Russian Foreign Ministry reported "the atmosphere has worsened sharply in central Kyiv." In a statement Tuesday, Russian authorities blamed the violence on Western governments, accusing them of encouraging "radical forces" among the protesters.
On Monday, Russia said it will release an additional $2 billion to Ukraine to support its moribund economy, a move seen as strengthening President Yanukovych's bid to remain in power. The money is part of a $15 billion loan promised by Russia.
Weeks of protests in Kyiv and other major Ukrainian cities have spawned widespread media coverage abroad and calls for more democracy in the former Soviet republic. German Chancellor Angela Merkel, a leading figure in the 28-member EU trade bloc, met Monday with two Ukrainian opposition leaders; boxer-turned-politician Vitaly Klitschko and Arseni Yatsenyuk.
Klitschko, writing ahead of the meeting in the German daily Bild, said the opposition was seeking EU support for sanctions against the Yanukovych government and help in curbing the powers of the Ukrainian president.
A Merkel spokesman was later quoted by Deutsche Welle as saying the chancellor voiced "sympathy for the legitimate concerns of the Ukrainian people." But he said Ms. Merkel did not agree with calls for sanctions at this time.
EU and U.S. officials have repeatedly said they are working with the International Monetary Fund on details of an aid package that analysts have described as rivaling or exceeding the Russian bailout deal. But no concrete offers have been made public.