At least four people have been shot dead and hundreds injured amid ongoing clashes with police over new laws limiting the right to protest in Ukraine, the head of protest movement's volunteer medical service, Oleg Musiy.
Ukraine's Interior Ministry earlier said it was investigating a death, the circumstances of which are not clear. Local media reports suggest the man may have fallen from a statue or monument.
Demonstrators have been rallying in the snowy streets since the weekend in protest against the laws that came into effect Wednesday.
Televised images Wednesday showed ongoing clashes between police and protesters who've massed around barricades on Hrushevskoho Street, near the burned-out shells of police buses.
The Interior Ministry said 195 police officers had been injured and 84 hospitalized since the situation turned violent Sunday.
The clashes are an escalation of weeks of largely peaceful public protests prompted by President Viktor Yanukovych's decision in November to spurn a planned trade deal with the European Union and turn toward Russia instead.
The European Union and United States have urged all parties in Ukraine to exercise restraint and find a democratic solution to the political crisis.
Russian Foreign Minister Sergey Lavrov also warned Tuesday that the situation in Ukraine was "getting out of control" and urged dialogue between all the parties.
Opposition meets with President
The leaders of three opposition factions met with Yanukovych and a government working group Wednesday to try to resolve the crisis, the President's official website said.
They are Vitali Klitschko, leader of the UDAR party; Arseniy Yatsenyuk, of the Fatherland party; and Oleh Tiahnybok, of the Freedom party, or Svoboda.
A statement on Yanukovych's website said the first stage of negotiations -- a meeting of more than three hours -- had ended.
Klitschko earlier accused Yanukovych's government of having the blood of protesters on its hands.
"Attacks and shooting at people by riot police is a conscious step of power to initiate a civil conflict," he is quoted as saying on the UDAR website.
"I urge Yanukovych to stop the troops immediately! Today the authorities respond to demands of people by shooting at them. And this is what cannot be forgiven."
UDAR also posted what it said was a joint statement by the three opposition factions saying Yanukovych and Interior Minister Vitaliy Zakharchenko bear direct responsibility for the deaths of protesters.
The U.S. ambassador to Ukraine, Michael McFaul, tweeted Wednesday that he was "watching with sadness" the events in Kiev.
The U.S. Embassy in Kiev said in a prepared statement that it has "revoked the visas of several Ukrainians who were linked to the violence" in response to actions taken against protesters in November and December.
"Because visa records are confidential under U.S. law the Embassy will not comment on individual cases," it said. "We are considering further action against those responsible for the current violence."