KYIV - Police and protesters clashed overnight in Ukraine, hours after embattled President Viktor Yanukovych tried to ease tensions by offering key government posts to two top opposition leaders.

A large crowd of protesters blocked a government building with police inside early Sunday in central Kyiv. Demonstrators threw stones and smoke bombs. Police responded with stun grenades and tear gas.

Ukraine Opposition Cool to Power-sharing Offer

Speaking to a large crowd Saturday in Kiev's Independence Square, Yatsenyuk said the opposition is "not afraid" of accepting more political responsibility, but that Yanukovych must still meet several key opposition demands and that talks will continue.

Ukraine Opposition Cool to Power-sharing Offer

Klitschko joined Yatsenyuk Saturday, saying Yanukovych has agreed to opposition demands, including the release of arrested protesters and the rescinding of recent changes to the constitution. Klitschko said, however, the protests will not stop.

Ukraine Opposition Cool to Power-sharing Offer

The opposition has demanded that both Yanukovych and Ukraine's number two leader, Prime Minister Mykola Azarov, step down. Protesters have also called for early elections.

The crisis was spawned by Yanukovych's November 21 decision to back out of a trade agreement with the European Union in favor of closer economic ties with Russia.

The decision resulted in a multi-billion-dollar bailout from Moscow that analysts say staved off near-certain bankruptcy for the impoverished country. But pro-European protesters were angered by the turn toward Moscow and took to the streets of the capital, Kyiv, where they have maintained a presence ever since.

The protests have spawned deadly clashes between protesters and police.

On Saturday, the opposition denied allegations that protesters are holding two police officers in Kyiv's occupied city hall.

Ukrainian officials have warned protesters to release the officers or face police action to free them.

Witnesses say the protest movement appears to have been infiltrated in recent weeks by members of a violent far-right militant group known as Right Sector, a loose alliance of nationalist organizations. The presence of the group adds a volatile element to the standoff that analysts say both the government and the mainstream opposition are struggling to contend with.

Anti-government forces were also occupying at least six regional capitals after storming government facilities across a wide swath of western Ukraine.