Ukrainian President Viktor Yanukovych threatened to crack down with full force on anti-government protesters after the bloodiest clashes in the country’s three-month standoffkilled at least 25 people on Tuesday.

A BBC correspondent noted that the violence was in fact the worst the country has seen in almost 70 years, since World War 2.

Police in the capital of Kiev launched a fresh attack on anti-government protesters although fighting eased somewhat Wednesday morning. They launched their latest assault on Independence Square, also known as the Maidan, shortly after 04:00 local time (02:00 GMT). Several tents were set on fire, and water cannon were used. A BBC correspondent said police had taken control of a corner of the square for the first time since December.

Meanwhile, Poland's Prime Minister Donald Tusk told lawmakers in Warsaw that “We may be witnessing the first hour of a civil war” in Kiev.

Live footage of Ukraine unrest:

The opposition “has crossed the line when they called people to arms,” Yanukovych said on his website Wednesday. “This is an outrageousviolation of the law. My advisers happen to be trying to talk me into a tough scenario, the use of force. But I have always considered the use of force a false route.”

Yanukovych, backed by Russia, is seeking to end the crisis that has rocked the country of 45 million. Activists last night repelled a police attempt to clear their main protest camp in central Kiev. Hundreds remained on Independence Square this morning, including reinforcements from the western city of Lviv, with squadrons of police ringing their burning barricades.

“We are dealing with an ongoing destruction of the country,” said Tusk. “If people are dying and being injured during protests, it’s the authorities who are responsible. There are no doubts about that in Kiev.”

The EU says it expects to place sanctions on those behind the violence.

The protests began in late November, when President Viktor Yanukovych rejected a landmark association and trade deal with the EU in favour of closer ties with Russia.