Opponents of Ukraine's president declared political autonomy in the major western city of Lviv on Wednesday after a night of violence that saw protesters seize public buildings and force police to surrender.

Raising the specter of a divided Ukraine split along an old historic, cultural and linguistic fault line, the regional assembly in Lviv, a bastion of Ukrainian nationalism near the Polish border, issued a statement condemning President Viktor Yanukovych's government for its "open warfare" on demonstrators in Kiev and saying it had taken executive power locally for itself.

In other signs of fraying central government control, Poland announced that Ukrainians had blocked the Korczowa border crossing near the city, while local media said that opposition groups in other western cities, including Khmelnitsky, Ivano-Frankivsk, Uzhorod and Ternopil, had also taken over public buildings.