Thick, dark smoke rose above the centre of the Ukrainian capital amid the boom of police stun grenades yesterday, as officers in riot gear sought to push demonstrators away from the city's main square.
This followed deadly clashes between police and protesters on Tuesday that left at least 25 people dead and hundreds injured and raised fears of a civil war.
After several hours of relative calm, confrontation flared up again, with hundreds of police massing on the edges of Independence Square, known as the Maidan, throwing stun grenades and using water cannons in a bid to disperse protesters. Thousands of activists armed with fire bombs and rocks held their ground, defending the square that has been a bastion and symbol for the demonstrators.
Watch: Police, protesters wage 'war' in deadly Kiev clashes
"We will not go anywhere from here," said opposition leader Vitali Klitschko, speaking to crowds from the stage as tents and tyres were in flames around him. "This is an island of freedom and we will defend it."
The violence on Tuesday was the worst in nearly three months of anti-government protests that have paralysed Ukraine's capital in a struggle over the identity of a nation divided in loyalties between Russia and the West. They were the worst in the country's post-Soviet history.
It prompted the European Union to threaten sanctions against Ukrainian officials responsible for the violence and triggered angry rebukes from Moscow, which accused the West of triggering the clashes by backing the opposition. President Viktor Yanukovych yesterday blamed the protesters for the violence and said the opposition leaders "crossed a line when they called people to arms".
The European Union appeared poised to impose sanctions as it called an extraordinary meeting of the 28-nation bloc's foreign ministers today. The foreign ministers of France, Germany and Poland will travel to Kiev to assess the situation before the meeting in Brussels.
In Lviv, a western city of 750,000 and capital of a region of 2.5 million, opponents of the president declared political autonomy after protesters seized public buildings and forced police to surrender.
Raising the prospect of Ukraine splitting along a historic cultural and linguistic faultline, the regional assembly in Lviv, a bastion of Ukrainian nationalism near the Polish border, issued a statement condemning Yanukovych's government for its "open warfare" on demonstrators in Kiev and saying it took executive power locally for itself.
In other signs of fraying central control for a government seen as close to business magnates from the Russian-speaking east, Poland said Ukrainians blocked the Korczowa border crossing near Lviv. And local media said opposition groups in other western cities, including Khmelnitsky, Ivano-Frankivsk, Uzhorod and Ternopil, also took over public buildings.
Overnight in Lviv, hundreds of people took part in protests as demonstrators fought riot police in central Kiev, nearly 500 kilometres away.
Additional reporting by Reuters