Anti-government protesters held their ground through a night of violent street clashes in the Ukrainian capital, despite police moving in to dismantle barricades erected in a street leading to government offices.
Police attempted to move in on the protest camp in Kiev early today, but faced fierce resistance from demonstrators who threw fire bombs and stones in their direction.
Police responded with stun grenades, tear gas and rubber bullets, and were able to dismantle a catapult and a barricade built by protesters before being pushed back to their original positions by the crowd.
Opposition leader Vitali Klitschko accused the government of paying thugs to delegitimise the protests through violence. He said the thugs, who were tasked with smashing windows and burning cars, were chased away by protesters.
Meanwhile, the White House blamed increased tensions in Ukraine on the country's government for failing to acknowledge people's legitimate grievances, and threatened sanctions if the use of violence continues.
National Security Council spokeswoman Caitlin Hayden said the US is deeply concerned about the violence in Kiev.
Anti-government protests in the capital escalated into street battles with police on Sunday in a sharp escalation of Ukraine's two-month political crisis.
Ms Hayden said Ukraine is weakening the foundations of its democracy by criminalising protests.
And she called on the government to repeal recent laws limiting protests, remove riot police from central Kiev and start talking to the opposition.
The White House said the US is considering sanctions among other steps if the government uses violence, echoing a warning from the State Department last month.