Ukraine's opposition Wednesday pressed for more concessions from President Viktor Yanukovych to resolve a deadly political crisis, including an amnesty for jailed activists, after securing the resignation of the prime minister and his entire government.
EU foreign policy chief Catherine Ashton was expected to hold talks on the crisis in Kiev, shadowed by a warning to the West by Russian President Vladimir Putin not to meddle in Ukraine's internal affairs.
The United States was also keeping a close watch on the situation, with Vice President Joe Biden speaking to Yanukovych in a telephone call and President Barack Obama backing protesters in his State of the Union address.
A day after scrapping anti-protest laws passed January 16 that had ignited the current spike in tensions, Ukraine's parliament was due to meet in a new extraordinary session starting at 0900 GMT to debate an amnesty for jailed activists.
Deputies had been unable to vote on the amnesty a day earlier after negotiations became bogged down over the authorities' insistence that protesters should vacate seized buildings and streets in Kiev before anyone was released.
Dozens of activists have been arrested since clashes broke out 19 January that resulted in the fatal shooting of three protesters.
The security forces have insisted they were not to blame for the killings, a claim met with incredulity by activists.
The scrapping of the anti-protest laws came on a dramatic day which also saw the resignation of Prime Minister Mykola Azarov, a Yanukovych loyalist, and his entire cabinet in an effort to ease the crisis.
First Deputy Prime Minister Sergiy Arbuzov, who is also close to Yanukovych, will take over as premier in a caretaker role until a replacement is named. Some analysts floated the idea that a pro-opposition tycoon, Petro Poroshenko, might step into the post full time.
The concessions were the biggest steps back made by the authorities to placate protesters who have occupied streets and official buildings in the centre of Kiev for over two months but the opposition made clear it wanted more.
Azarov's resignation "was an important step but too late," opposition Fatherland party leader Arseniy Yatsenyuk told Channel 5 television Tuesday.
The UDAR (Punch) party leader and world boxing champion Vitali Klitschko said: "Azarov should have resigned two months ago.... Now the logical step would be the resignation of Viktor Yanukovych."
Jailed former prime minister Yulia Tymoshenko, who the opposition says is the victim of a political vendetta by Yanukovych, said Tuesday's concessions were the "first real result from the fight of people who took to the streets".
But she added: "It is not enough. Do not stop!"
Ukrainian media also quoted ruling Regions Party MPs as saying that changes to the constitution to return to the version set out in 2004 which give the presidency fewer powers may also be debated.
Inna Bogoslovska, a former Regions Party MP who changed sides in the crisis, told Channel Five that she had understood that the authorities had been unable to agree the imposition of a state of emergency due to the opposition of kingpin pro-government tycoons Rinat Akhmetov and Sergiy Tigipko.
The protests erupted in late November as a pro-Europe movement after the government ditched an integration deal with the European Union under Russian pressure.
But they swelled into an all-out drive to unseat Yanukovych and became increasingly radical as protesters flooded into Kiev from the anti-government west of the country.
Protesters, some from right-wing radical groups, remain camped out in the sprawling military-style enclosure that has taken over much of the city centre and is surrounded by barbed wire and barricades topped with pikes.
Obama on Tuesday gave high-level support to the protestors in Ukraine, declaring: "In Ukraine, we stand for the principle that all people have the right to express themselves freely and peacefully, and have a say in their country's future."
The White House said that Biden welcomed "progress made today" in Ukraine and "strongly encouraged President Yanukovych to continue to work with the opposition to find compromises critical to a peaceful solution".
Attending an EU-Russia summit in Brussels shadowed by tensions over Ukraine, Putin warned his hosts against meddling.
"The more intermediaries there are, the more problems there are," he said.
But in a conciliatory move, the Kremlin leader also emphasised that Russia "will not" review its $15-billion (11-billion-euro) bailout for Ukraine, whoever ends up in charge in Kiev.
Canada, which has a large Ukrainian minority, praised the courage of protesters and on Tuesday said it would refuse entry to any government officials linked to the crackdown.
As concern mounted over the effect on the already fragile economy of the turmoil, Standard & Poor's on Tuesday downgraded the country's credit risk rating by one notch to CCC+ from B-, citing political instability.