Ukrainian President Viktor Yanukovych on Friday signed a law offering an amnesty to jailed opposition activists and repealed controversial laws cracking down on protests, his office said.

The amnesty bill passed by parliament on Wednesday gives protesters a 15-day deadline to vacate the public buildings they have occupied in order for it to be implemented.

President Vladimir Putin's advisor said on Friday that Ukrainian President Viktor Yanukovych would lose power as a result of the ex-Soviet state's political crisis unless he "quashes the rebellion".

"He (Yanukovych) is currently in the situation of a creeping coup and because he is the guarantor of the Constitution, security and integrity of Ukraine, then the president has no choice," Kremlin economic aide Sergei Glazyev said in remarks released on Friday.

Ukraine's army on Friday called on embattled President Viktor Yanukovych to take "urgent steps" to ease the political crisis in the ex-Soviet country.

"Laying out their civil position, servicemen and employees of Ukraine's armed forces... called on the commander-in-chief to take urgent steps within the limits of existing legislation with a view to stabilizing the situation in the country and reaching consent in society," a statement from the defense ministry said.

A Ukrainian opposition activist who went missing more than a week ago has been found badly beaten, saying his captors cut off his ear and drove nails through his hands.

Dmytro Bulatov, a 35-year-old activist from the Avtomaidan group that organised protests against President Viktor Yanukovych, stumbled into a village outside Kiev more than a week after his wife first reported him missing.

Russia on Friday slammed as a "circus" U.S. Secretary of State John Kerry's planned weekend meeting with Ukrainian opposition leaders.

The top U.S. diplomat is due to meet former boxing champion Vitali Klitschko, leader of the UDAR (Punch) party and opposition leader Arseniy Yatsenyuk on the sidelines of the annual Munich Security Conference on Saturday.

U.S. Secretary of State John Kerry will meet Ukrainian opposition leaders for the first time on Saturday in a major show of support for pro-democracy protesters locked in a deadly two-month stand-off with President Viktor Yanukovych.

Among those slated to hold talks with the top U.S. diplomat on the sidelines of the Munich Security Conference are former boxing champion Vitali Klitschko, who leads the UDAR (Punch) party, and opposition politician Arseniy Yatsenyuk.

Those responsible for acts of violence and abductions in Ukraine must be identified and held accountable, Poland's premier Donald Tusk and European Commission chief Jose Manuel Barroso said Thursday.

During a joint and brief news conference held after talks on the crisis in Ukraine, the Polish premier also warned that there could be no European Union assistance to Kiev until the authorities called a halt to the violence.

Stretched out on a makeshift mattress, Petro rubbed his eyes, still swollen with sleep, and sighed: "We must hold on in order to get results."

After two months of occupying Kiev's city hall, Ukrainian protesters may look hollow-eyed but are keeping up a ceaseless vigil.

President Viktor Yanukovych on Thursday savaged the opposition for inflaming tensions in Ukraine's protest crisis after he unexpectedly went on sick leave with no end in sight to the turmoil.

In an address to the nation, Yanukovych turned on the "irresponsible" opposition which has refused to abandon over two months of protests despite a string of concessions, including an amnesty for jailed demonstrators.

Ukrainians demanding the president's resignation dug their heels in at protest sites across the country Thursday, despite a third major concession in two days by the regime.

At a late parliament session Wednesday, an amnesty bill that would free activists was passed with the ruling Regions Party but opposition MPs defiantly refused to vote.