Ukraine’s first post-independence president has warned the country is on the “brink of civil war”.
Leonid Kravchuk, president from 1991 to 1994, urged parliament to “act with the greatest responsibility” as it debates an amnesty for detained protesters.
President Viktor Yanukovych wants any amnesty to be conditional on protesters leaving official buildings and dismantling barricades.
The EU’s foreign policy chief said all parties must hold “real dialogue”.
Former Ukrainian President Leonid Kravchuk’s dramatic warning that the country stood on the “brink of civil war” and is gripped by “revolution” did not reveal any secrets.
But it was a timely reminder of what could lie at the end of Ukraine’s bitter political standoff if a peaceful resolution isn’t found soon.
Many might dispute that the divisions in Ukraine’s society are as clear cut as east-west, or Russian-speaking and Ukrainian-speaking, and, to be sure, much of this is mitigated by other aspects such as differences in outlook between the young and old.
Nevertheless, it is undeniable that the country is dangerously divided into, roughly speaking, two mutually antagonistic, and very often mutually-uncomprehending, political camps.
But the immediate risk is not civil war. Many observers question whether the people in the east are ready to risk their lives for President Viktor Yanukovych’s government. But widespread violence is very real – and this in turn could balloon eventually into a conflict that embraces more and more of Ukrainian society.
Catherine Ashton, who is holding talks in Kiev with the president and opposition leaders, said she was shocked by the unrest, and that there was “no question that the importance of finding a quick and peaceful way forward is on everyone’s minds”.
“The solution has to be found that’s going to help move the country forward, and it needs to be a political process that is engaged in quickly and properly by everyone,” she said.
“The responsibility is inevitably going to fall on government to do that as quickly as possible.”
The protests began in November after Mr Yanukovych reversed a decision to sign a long-awaited trade deal with the EU, instead favouring stronger ties with Russia.
At least five people have been killed and a number of government buildings across the country have been occupied. Hundreds of people remain on the streets of the capital, Kiev.
German Chancellor Angela Merkel urged Russian President Vladimir Putin on Wednesday to push for a “constructive dialogue” between the opposition and government to defuse the crisis.
Following a telephone call with Mr Putin, she said that “all parties must accept their responsibility to stabilise the country”.
The Kremlin later re-iterated its stance of recent days that any outside interference in Ukraine was “unacceptable”.
Last year, Moscow promised a $15bn (£9.2bn; 10.9bn euros) loan to Ukraine, a move widely seen as a reward for Kiev’s rejection of the EU deal.
Mr Putin has insisted he will honour the deal, but there are suggestions now that Moscow could delay delivering the payments until a new government is formed.
A policeman was shot dead in Kiev on Wednesday, said officials. It was not immediately clear whether the shooting was related to the protests.
Ukraine’s parliament is debating an amnesty for the scores of protesters detained since demonstrations began, in the hope of calming the unrest.
Mr Kravchuk told MPs: “All the world acknowledges and Ukraine acknowledges that the state is on the brink of civil war.
“It is a revolution. It is a dramatic situation in which we must act with the greatest responsibility,” he said in an emotional address that earned him a standing ovation.
MPs are expected to vote on the bill later, but the BBC’s David Stern in Kiev says it remains unclear whether it will pass, and if the protesters will accept its conditions.
Opposition leader Arseniy Yatsenyuk has said the requirement that protesters leave their main protest camp in Kiev was “unacceptable”.