LVIV (AFP) - Thousands of protesters on Thursday stormed the offices of governors in several regions of western Ukraine, in a new wave of anti-government anger in the provinces.

Governors of Ukrainian regions are appointed by President Viktor Yanukovych and have now become targets of protesters in the west of the country which is strongly pro-opposition.

Around one thousand protesters held a demonstration outside the offices of Lviv region governor Oleg Salo, shouting "revolution" and calling for his resignation.

They pushed past the guards and stormed the building and went through its corridors in search of Mr Salo, an AFP correspondent in the regional capital Lviv said.

Mr Salo was not in his office but the protesters later found him and surrounded him, saying they would not depart until he resigned. The governor then signed his resignation and handed it to the protesters. "I ask to be freed of my duties," he said in the document.

But Mr Salo later withdrew his resignation, saying he had made the move under pressure and it was invalid. The Kiev-appointed governor is an unpopular figure in Lviv and its region, a Ukrainian- speaking area which is hugely supportive of the protest movement.

Thousands of people from the Lviv region have gone to Kiev to take part in the rallies on Independence Square.

Amid a chaotic situation in the historic city next door to Poland, around 500 protesters are preparing to stay overnight in the regional administration building. They are arranging "self-defence units" of over 200 men and 50 women and planning not to let Mr Salo work on Friday.

Moreover there are plans to announce an executive committee and to take over state administration functions in the region Friday.

Similar protest actions aiming to remove governors were also under way in other western regions of Ukraine, where Mr Yanukovych garnered very little support when he was elected in 2010. Most people in the west are Ukrainian-speaking and regard the Soviet rule of Ukraine as an occupation.

Yanukovych, who hails from the Donbass region in the east of the country which is traditionally Russian-speaking and more pro-Kremlin, is widely despised in the western area.

Several hundred protesters occupied the governor's administration in the neighbouring region of Ternopil, local media said. Police forces did not resist and there were no officials in the building at the time.

Protesters are occupying the ground floor of the Rivne regional state administration building and asking police forces to leave.

A similar standoff was also reportedly in progress in the Zhytomyr region west of Kiev as well Khmelnitsky to the southwest.

In the Cherkassy region south of Kiev, thousands of protesters stormed the governor's state administration building and made a fire using the furniture, the Ukrainska Pravda news site said.

The situation in the provinces provides a new headache for Mr Yanukovych as he seeks to survive mass protests against his rule in Kiev that have now descended into violent clashes.

Ukrainians in the west see their country at the heart of Europe and were infuriated when Mr Yanukovych failed to sign a pact for closer integration with the European Union last year.