This post was updated at 8:52 p.m. ET
Riot police stormed the main anti-government camp in central Kiev, the capital of Ukraine, on Tuesday. They fought with demonstrators armed with clubs and wearing helmets fought back. More than a dozen people were killed, including five policemen, according to AP and the BBC.
Opposition leaders met late in the day with President Viktor Yanukovych, but left without an agreement.
Vice President Joe Biden called Yanukovych earlier Tuesday, urging him to pull back his forces.
Here's more from Reuters on what's happening:
"Despite Western demands for restraint and dialogue, the state security service first set a deadline for the demonstrators to end disorder or face 'tough measures', and then the police advanced into Independence Square, the centre of the protest campaign.
"Protesters responded with petrol bombs, fireworks and stones, as police moved slowly forward. Live television footage showed officers throwing stun grenades at the protesters separated from them by a line of burning tents, tyres and wood."
Although police were gaining ground in Kiev's Independence Square, thousands of protesters remained to hear speeches from their leaders and sing their national anthem.
The Associated Press said police dismantled barricades on the perimeter of Independence Square and set some of the protesters' tents there on fire. (You can watch a live stream of what's happening in Kiev here).
Earlier Tuesday, the protests against the government, which began last November, turned deadly. AP is reporting that 14 protesters and seven police officers were killed in the violence.
Reuters adds: "Many were killed by gunshot and hundreds more were injured, with dozens of them in a serious condition, police and opposition representatives said."
Biden called Yanukovych to express "grave concerns" about the situation. Biden condemned violence on both sides, but said " the government bears special responsibility to de-escalate the situation," according to a White House statement.
Reporter David Stern, who is in the Ukrainian capital, tells NPR's Robert Siegel that Tuesday's violence is an escalation.
"The situation seems to be escalating even further, which is probably what most people are worried about most of all because it doesn't seem it will ever end," he says, "and there is a question of what will happen to Ukraine as a whole if this does spread ... beyond the capital."
At issue is Ukraine's future direction. Late last year, Yanukovych rejected a trade deal with the European Union in favor of closer ties with Moscow, leading to protests against his government.
The New York Times reports on Tuesday's unrest:
"The violence began early on Tuesday when antigovernment activists moved out of their barricaded zone around Independence Square and advanced into a government-controlled district, battling riot police officers with stones and Molotov cocktails in the worst clashes in nearly a month. A group of young militants occupied and set fire to the headquarters of the ruling Party of Regions. ...
"Much of the violence early Tuesday took place along Instyuts'ka Street near Ukraine's Parliament building and the main offices of the government. Protesters hurled stones at police officers sheltering behind a barricade of blazing vehicles while ambulances, sirens wailing, rushed to help people injured in the clashes."
Polls show Ukrainians evenly divided in their views of the protests.