U.S. Vice President Joe Biden called Ukraine's President Viktor Yanukovych on Thursday to press for a peaceful resolution to the country's political crisis after deadly violence between police and protesters.

Before announcing the call, the White House had put the blame for the violence squarely on government forces in Kiev, but did welcome news of talks between opposition leaders and Yanukovych.

A member of Ukraine's elite Berkut riot police force assaulted and humiliated a naked protester after he was detained in freezing cold temperatures in Kiev, according to a video posted Thursday.

The Ukrainian interior ministry swiftly apologized for the horrific incident, which recalled notorious prisoner abuse scandals like that at Abu Ghraib prison in Iraq.

EU foreign policy chief Catherine Ashton said Thursday she will meet Ukrainian President Viktor Yanukovych and opposition leaders in Kiev next week in an effort to promote dialogue.

"I am convinced that, in light of the violent escalation of events, the EU has to reinforce the efforts in support of the political solution," Ashton said.

The prime mover in organizing Kiev opposition protesters in bloody clashes with the security forces has been a shadowy far-right group called Right Sector rather than Ukraine's established anti-government leaders.

The trio of opposition leaders who spearheaded two months of anti-government protests since late November were taken by surprise by the clashes that broke out on Sunday, blaming the authorities for the unrest but steering clear of condoning violence by the protesters.

German Chancellor Angela Merkel said Thursday that Ukraine must safeguard the lives of pro-EU demonstrators following deadly clashes with security forces but rejected calls for fresh sanctions against Kiev.

Merkel sharply condemned the violence, which activists say has left five dead, as well as new Ukrainian legislation barring protests, as the EU debates possible reprisals.

The last Soviet leader Mikhail Gorbachev on Thursday appealed to Russian President Vladimir Putin and U.S. President Barack Obama to broker peace talks to end the deadly violence rocking Ukraine.

"I am sure that you are capable of achieving this aim. The sides fighting each other must sit down together for talks," the 82-year-old statesman said in an open letter published on the website of his Gorbachev Foundation.

Russia will not intervene in the raging anti-government protests in Ukraine and believes its leadership will find a way out, President Vladimir Putin's spokesman Dmitry Peskov said Thursday.

"We consider we do not have the right to intervene in any way in the internal affairs of our brother Ukraine. That's unacceptable and Russia has not done this and will not do it," Peskov said in an interview published on the website of Komsomolskaya Pravda daily.

Ukrainian President Viktor Yanukovych on Thursday demanded an extraordinary session of parliament to ease the crisis in the country after five days of deadly clashes between protesters and security forces.

The three main opposition leaders were to hold crisis talks with Yanukovych, as world boxing champion and UDAR (Punch) party leader Vitali Klitschko brokered a truce in the violence between protesters and police.

Ukraine's former master Russia on Wednesday slammed "outside interference" in its neighbor's affairs and accused the radical opposition against President Viktor Yanukovych of crudely violating the constitution.

"Ukraine's legitimate authorities face outside interference in its internal affairs," Russian Deputy Foreign Minister Grigory Karasin told Interfax, referring to a number of statements from the United States and the European Union.

The head of the European Union executive, Jose Manuel Barroso, warned Ukraine of "possible" reprisals after the deaths of two pro-EU protesters Wednesday but stopped short of announcing sanctions.

"We are shocked ... and deplore in the strongest possible terms the use of force and violence," Barroso said, squarely laying responsibility "to de-escalate this crisis" on the Ukrainian authorities.