New clashes as Ukraine's president tries to tempt opposition

* Confrontation follows offer of top posts to opposition

* Opposition says will keep up demands for early election

* Ukraine's U-turn from Europe has divided country

* Unrest spreads to traditionally pro-Yanukovich east

By Pavel Polityuk and Natalia Zinets

KIEV, Jan 26 (Reuters) - Police clashed with protesters in central Kiev on Sunday and the fate of Ukraine's government was uncertain after embattled President Viktor Yanukovich offered important posts to opposition leaders, including the role of prime minister.

One of the president's main foes described his offer as a "poisoned" attempt to divide the opposition and kill off mass protests. The demonstrations erupted late last year when Yanukovich ditched landmark agreements with the European Union and opted instead for closer ties with Russia.

Emboldened opposition leaders said they would press for more concessions, including early elections, setting the stage for a tough political battle when parliament meets for a special session on Tuesday.

The two-month standoff has sparked the worst violence in Ukraine since it won independence in 1991 as the Soviet Union collapsed. At least six people have been killed, according to the prosecutor's office and medics, and the crisis has deepened tension between Russia and the West.

For the opposition, accepting Yanukovich's offer to serve under him in a revamped government carries the risk of breaking faith with thousands of peaceful demonstrators as well as alienating more radical protesters over whom it has only tenuous control.

"Yanukovich's offer always appeared as a poison chalice for the opposition - meant to divide the opposition, and boost his chances in the March 2015 presidential election," Tim Ash of Standard Bank said.

In violence on Sunday, a few thousand protesters tried to storm an ornate cultural centre where hundreds of security forces personnel were gathered in central Kiev, a few hundred metres (yards) from the hub of weeks of opposition protests on Independence Square.

In a two-hour pre-dawn confrontation, demonstrators threw stones and smoke bombs while police fired stun grenades and sprayed water into the crowd.

Police and security forces later left the building, its windows shattered, and streamed out through a corridor created by the crowd after an opposition leader, Vitaly Klitschko, arrived at the scene and helped to negotiate a solution.

The opposition planned a prayer ceremony later on Sunday for protesters who have been killed. A coffin bearing the body of one of them, Mykhailo Zhyznevsky, was borne through the streets of Kiev before his burial, with several hundred people marching behind.