Thousands of anti-government protesters held out on the streets of Kiev on Thursday, as a 24-hour ultimatum by the opposition calling for President Viktor Yanukovych to step down approached, dpa reported.
In a first concession, parliament said it would discuss whether the government should resign at an extraordinary session next week.
A new round of talks between opposition leaders and Yanukovych on Thursday ended with no breakthrough.
Opposition leader Vitaly Klitschko said the main demands were to end "the terror and the persecution of people" as well as the resignation of the government, the Interfax news agency reported.
The former boxing champion asked demonstrators to be patient, while Yanukovych promised to free within three days the estimated 100 protesters who were arrested. After fatalies among the anti-government demonstrators, the pro-Russian camp in Kiev signalled a willingness to give in.
The call for the president to step down came after three activists were killed. Two died in Kiev of gunshot wounds. The opposition blamed those killings on police, but the Interior Ministry said that officers had not been issued guns.
The body of a third activist, Yuri Verbytskyi, was discovered with marks of torture. Police said that the bruises could not be linked to his death and that the activist died of hypothermia.
Some opposition members put the death toll at seven.
The deaths were the first since the crisis over Yanukovych's rejection of a partnership deal with the European Union erupted in November.
There were also reports of violence against journalists. A reporter for Russia's lenta.ru news site, Andrei Kiselyov, was beaten by police, said colleagues who posted a photo of his badly bruised face online.
Outside the capital, protesters stormed or encircled a number of regional administrations. In the western region of Lviv, the Yanukovych-appointed governor, Oleh Salo, was forced to sign a resignation letter. Salo later retracted, saying that he had signed under duress.
The opposition stepped up the protests at the weekend after parliament approved laws that curb free speech, establish new penalties for unlawful protests and make it easier to strip legislators of their immunity.
The government has blamed the protesters for the violence. Prime Minister Mykola Azarov said Thursday that the opposition activists were "rebels" trying to overthrow the government.
Speaking at the World Economic Forum in Davos, Azarov said that early presidential elections were "absolutely unrealistic," Interfax reported. Yanukovych's current five-year term expires in spring 2015.
The tense situation plunged Ukraine into its deepest crisis since the Orange Revolution of 2004-2005. That was touched off when pro-Western protesters denounced the results of a run-off presidential election rigged in favour of Yanukovych.
EU Commission President Jose Manuel Barroso urged Yanukovych in a telephone call to immediately start a dialogue with the opposition.
Barroso said the EU was ready to mediate in the crisis, his spokesman Olivier Bailly told reporters in Brussels. Stefan Fule, the EU Commissioner for neighbourhood policy, will travel to Kiev Friday, and foreign policy chief Catherine Ashton is to visit next week.
Bailly also said that sanctions against Ukraine was "only an eventuality if the violence continues."
US Vice President Joe Biden called Yanukovych and urged an immediate de-escalation of the standoff by taking steps to end the violence and address protesters' concerns.
"While emphasizing that violence by any side is not acceptable, the vice president underscored that only the government of Ukraine can ensure a peaceful end to the crisis and further bloodshed would have consequences for Ukraine's relationship with the United States," the White House said. The US indicated sanctions are possible if violence continues.
German Chancellor Angela Merkel ruled out sanctions, saying they are "not the order of the day." She also phoned Yanukovych and urgently appealed for a serious dialogue with the opposition.
Russia, which has agreed to sell Ukrainian natural gas at a discount and provided the government a multi-billion-dollar credit line, has accused the EU and the United States of fueling the protests.
President Vladimir Putin's spokesman Dmitry Peskov said in an interview published Thursday that any interference in Ukraine's internal affairs was unacceptable.
Without naming any country, Peskov said that Moscow resented it "when foreign ambassadors in Kiev tell the government in Ukraine what it should do."