As fires burned in central Kiev for a second night, Ukraine's embattled president replaced the chief of the country's armed forces and the military announced it could take part in a national anti-terrorist operation to restore order.
The move, announced in a decree from President Viktor Yanukovych, came a day after 25 people were killed and nearly 250 injured in clashes between police and protesters at the sprawling protest camp in central Kiev.
The announcement boded ill for any reconciliation efforts between Mr Yanukovych's government and the protesters who have demanded his resignation for nearly three months. Officials have often referred to the demonstrators as "terrorists".
It also came ahead of an emergency meeting on Thursday in Brussels, where European Union ministers said they would consider sanctions against those responsible for violence in Ukraine.
President Barack Obama said on Wednesday "there will be consequences" for violence in Ukraine if people step over the line.
He said that includes making sure that the military doesn't step into a situation that civilians should resolve.
Mr Obama said the US condemns the violence in the strongest terms. The US holds Ukraine's government primarily responsible to ensure it's dealing with peaceful protesters appropriately.
The violence this week was the worst in nearly three months of anti-government protests that have paralysed Kiev, Ukraine's capital. The opposition and Mr Yanukovych's government are locked in a stalemate over the identity of their nation of 46 million, which is divided in its loyalties between Russia and the West.
Ukraine's top security agency accused protesters on Wednesday of seizing hundreds of firearms from its offices and announced a nationwide anti-terrorist operation to restore order. The Defence Ministry said the army could take part in the operation.
Demonstrators, meanwhile, forced their way into the post office on Independence Square, also known as the Maidan, after a nearby building they had previously occupied was burned down on Tuesday in fierce clashes with riot police. Thousands of activists armed with fire bombs and rocks had defended the square, which has become a key symbol of the protests.
Black smoke from the sprawling, now-burnt opposition camp was still rising above the center of Kiev 24 hours later.
The shocking escalation of violence has prompted the European Union to threaten sanctions against Ukrainian officials responsible for the bloodshed and triggered an angry rebuke from Moscow, which accused the West of setting off the clashes by backing the opposition.
In Paris, Foreign Minister Laurent Fabius told reporters in a joint appearance with US Secretary of State John Kerry that he and his counterparts from Germany and Poland would meet both sides in Ukraine ahead of the EU meeting on possible sanctions.
He said he hoped the two sides "will find a way for dialogue".
Possible sanctions include banning leading officials from traveling to EU nations or freezing their assets there. Travel bans and assets freezes for the powerful oligarchs who back Mr Yanukovych could prompt them to pressure him to change course.
But the bad blood in Ukraine now runs so high it has fuelled fears the nation could be sliding toward a messy break-up. While most people in the country's western regions resent Mr Yanukovych, he enjoys strong support in the mostly Russian-speaking eastern and southern regions, where many want strong ties with Russia.
Neither side now appears willing to compromise, with the opposition insisting on Mr Yanukovych's resignation and early elections and the president prepared to fight till the end.
Amid a stagnating economy and soaring corruption, Ukrainians have been angered to see that Yanukovych's close friends and family have risen to top government posts and amassed fortunes since he came to power in 2010. Mr Yanukovych's son, Oleksander, a dentist, has become a financial and construction magnate worth 187 million dollars (£112m) , according to Forbes Ukraine.
Mr Yanukovych blamed the protesters for the violence and said the opposition leaders "crossed a line when they called people to arms."
"I again call on the leaders of the opposition ... to draw a boundary between themselves and radical forces, which are provoking bloodshed and clashes with the security services," the president said in a statement. "If they don't want to leave (the square) - they should acknowledge that they are supporting radicals. Then the conversation with them will already be of a different kind."
He also called for a day of mourning on Thursday for the dead.
Opposition politician Oleh Lyashko warned that Mr Yanukovych himself was in danger if he does not offer some concessions.
"Yanukovych, you will end like (Muammar) Gaddafi," Mr Lyashko told thousands of angry protesters. "Either you, a parasite, will stop killing people or this fate will await you. Remember this, dictator!"
The protests began in late November after Mr Yanukovych turned away from a long-anticipated deal with the EU in exchange for a 15 billion dollar (£9bn) bailout from Russia. The political manoeuvering has continued since, with both Moscow and the West eager to gain influence over this former Soviet republic.
The Kremlin said it put the next disbursement of its bailout on hold amid uncertainty over Ukraine's future and what it described as a "coup attempt."
European Commission President Jose Manuel Barroso, meanwhile, called for "targeted measures against those responsible for violence."
"It was with shock and utter dismay that we have been watching developments over the last 24 hours in Ukraine," he said.
Meanwhile, in the western Ukrainian city of Lviv, where most residents yearn for stronger ties with the EU and have little sympathy for Mr Yanukovych, protesters seized several government buildings, including the governor's office, police stations, and offices for prosecutors, security officials and the tax agency. They also broke into an Interior Ministry unit and set it on fire.
In another western city, Lutsk, protesters handcuffed the regional governor, a Yanukovych appointee, and tied him to the stage on a central square after he refused to resign.
In the city of Khmelnitsky, three people were injured when protesters tried to storm a law enforcement office.
Government buildings were stormed or besieged in other western cities.