KIEV, Ukraine (CBSNews.com) -- Enraged protesters stormed government offices in three western Ukraine cities Thursday, forcing one governor to write a letter of resignation, as demonstrations against the pro-Russian president and his allies intensified outside the smoldering capital.
Kiev, the capital, has been the epicenter of two months of protests against President Viktor Yanukovych that have grown increasingly violent this week. Opposition leaders had given Yanukovych a deadline of Thursday evening to make concessions or face renewed clashes there, and they quenched the barricade fires that had coated the capital in black smoke in a tenuous cease-fire.
After an hours-long meeting between opposition leaders and Yanukovych, Olha Lappo, a spokeswoman for top opposition leader Arseniy Yatsenyuk, said on her Facebook page that chances of ending the violence were high.
While the crowds waited for leaders to emerge from negotiations, Orthodox priests tried to maintain the shaky cease-fire at barricades.
Earlier, the president had called a special session of parliament next week to discuss the tensions, telling the parliament speaker: "The situation demands an urgent settlement." But there was no indication that the move represented a compromise, since the president's backers hold a majority of seats.
The protests began after Yanukovych turned away from closer ties with the European Union in favor of getting a bailout loan from Russia. They turned violent this week after he pushed through harsh anti-protest laws, rejecting protesters' demands that he resign and call new elections.
At least two protesters died Wednesday of gunshot wounds, a grim escalation that also galvanized anger in western Ukraine, where support for Yanukovych is virtually non-existent and most residents want closer ties to the 28-nation EU.
In Lviv, a city in near the Polish border 280 miles west of Kiev, hundreds of activists burst Thursday into the office of regional governor Oleh Salo, a Yanukovych appointee, shouting "Revolution!" and singing Christmas carols.
After surrounding him and forcing him to sign a resignation letter, an activist ripped it out of Salo's hands and lifted it up to the cheers and applause of the crowd. Salo later retracted his signature, saying he had been coerced.
Meanwhile, hundreds of protesters smashed windows, broke doors and stormed into the governor's office in the city of Rivne, shouting "Down with the gang!" - a common reference to Yanukovych's government. Once inside, they sang the national anthem.
Angry crowds also besieged government offices in two other western regions.
Meanwhile, anger spread after a video was released online appearing to show police abusing and humiliating a naked protester in what looked like a location close to the site of the Kiev clashes.
In the video, a young man, his body covered in multiple bruises, wearing nothing but socks, is made to stand on the snow in freezing temperatures, while a policeman punches him in the head and others force him to pose for photos.
The Interior Ministry issued a statement, apologizing "for the impermissible actions of people wearing police uniforms" and launched an investigation into the incident.
In Washington, White House press secretary Jay Carney told reporters that the Obama administration condemned the violence and called on the government to refrain from adding to it.
"This situation arose because of the refusal of the Ukrainian government to listen to and take seriously the concerns of the Ukrainian people," Carney said, adding that the U.S. supported dialogue between the government and the opposition.
The protests have been centered on Kiev's main square, where demonstrators have defended a large tent camp for nearly two months. On Wednesday, riot police moved to dismantle barricades erected next to a government district nearby and two people were fatally shot in the clashes.
The opposition has blamed the deaths on authorities, but Prime Minister Mykola Azarov said Thursday that the two men's wounds were caused by hunting rifles, which the police do not possess.
The opposition maintains that as many as five people died in Wednesday's the clashes, but say they have no evidence as the bodies were removed by authorities.
Azarov, Yanukovych's staunch ally, maintained a harsh stance against the protesters, calling their actions an attempted coup.
"It's not the opposition - it's rebels who are acting against us," Azarov said at the World Economic Forum in the Swiss town of Davos.
The Interior Ministry said Thursday that 73 people have been detained, 52 of whom are being investigated for "mass riots" - a new criminal charge that carries a prison sentence of up to eight years.
Reaction from the West and neighboring Russia has been mixed.
The United States has revoked the visas of Ukrainian officials linked to violence and threatened more sanctions. On Thursday, it welcomed Yanukovych's face-to-face talks with the opposition as a "necessary first step toward resolving this crisis."
EU Commission President Jose Manuel Barroso said Thursday that if the situation in Ukraine does not stabilize, the EU "would assess possible consequences in its relationship." Barroso also said he had received assurances from Yanukovych that the Ukrainian leader did not foresee the need to impose a state of emergency.
German Chancellor Angela Merkel said her nation doesn't think this is the time to consider sanctions against the Ukrainian government but added that it must comply "with its obligations to secure fundamental democratic rights."
"We are extremely concerned - not just concerned, appalled - about the way in which laws have been pushed through that raise questions over these fundamental freedoms," Merkel said.
Russia, in turn, accused the West of meddling in Ukraine's affairs.
"We feel regret and indignation about the obvious foreign interference in the developments in Kiev," Russian President Vladimir Putin's spokesman, Dmitry Peskov, told the daily Komsomolskaya Pravda.
The protesters, meanwhile, said they would give peace a chance - a brief one.
"We're ready to wait so that new victims don't appear," said 30-year-old demonstrator Anatoly Lovchenko. "But if the government doesn't listen to our demands, we'll start up again."
© 2014 CBS Interactive Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.