* Pro-Russian demonstrators besiege deputies in east
* Protesters seek immediate split from Kiev
* Deputies agree to back them but give no specifics
* Russian speakers in region want more autonomy, but wary (Updates with police comment paragraphs 9-10)
By Lina Kushch
DONETSK, Ukraine, March 3 (Reuters) - Pro-Russian demonstrators occupied the regional government building in east Ukraine's city of Donetsk on Monday, besieging lawmakers as they voted to support the protesters but stopped short of meeting their demands for a split from Kiev.
The chaotic scene in the heart of Ukraine's Russian-speaking east was one of the boldest actions yet by pro-Russian youths after several days of rallies in eastern and southern cities that Kiev says are organised by Moscow as a pretext to invade.
The protesters stormed the building and reached the second floor where the regional council sits, despite efforts to keep them out by switching off lifts and sealing stairwell doors.
The confrontation revealed a rift in the mainly Russian speaking region between locals who want less meddling from Kiev in local affairs and the protesters, who Ukraine says are led from Moscow and who are calling for the region to break away.
Hundreds of demonstrators, chanting "Putin, come!" entered the building through a side door after clashing with police guarding the front of the building, a Reuters photographer said. Windows were smashed, making it possible for some to reach the second floor.
Reporters inside, who sheltered on the fourth floor after the first floor was overrun, were eventually escorted out of the besieged building by police. The protesters checked documents to prevent employees and lawmakers from leaving.
The 11-storey building has been flying the Russian flag, rather than the Ukrainian flag, for three days, with pro-Russian demonstrators staging daily rallies outside.
Barricaded inside the building, the local lawmakers voted 98-3 in favour of a declaration that pledged "support for the popular initiatives of the residents of the Donetsk region, put forward at demonstrations," according to a text of the resolution on the regional government website.
However, the text fell short of demands of the protesters, led by a man named Pavel Gubarev, who has declared himself "people's governor" of the region. He had demanded deputies declare the government in Kiev illegitimate, put all security forces under regional control, withhold taxes from Kiev and a host of other measures.
NO REFERENDUM QUESTION
The resolution called for a referendum in the region, but did not say what question would be asked or when it would be held. The protesters want a vote on March 30 that would declare the region sovereign. Kiev says any such vote would be illegal.
The resolution also called for "public formations for the maintenance of public order", and recognised "historical, spiritual and cultural" links between the region and Russia.
Regional police chief Roman Romanov said police had opened a criminal case over the occupation of the building, two floors of which were still occupied by protesters by nightfall. He did not identify any suspects.
Romanov said police had failed to defend the building because they sought "to avoid bloodshed". Asked who he accepted as the legitimate authorities, he said: "I have given an oath to the Ukrainian people."
Many Russian-speakers in eastern Ukraine are angered by the dominance of Ukrainian-speaking westerners in the new authorities in Kiev and want greater autonomy, but they are also wary of potential provocation by Moscow.
Russian forces have already taken control of Ukraine's Crimea region, an isolated Black Sea peninsula, and Moscow has threatened to invade Ukraine to protect Russian speakers from what it says is a nationalist new government in Kiev.
Kiev says pro-Russian demonstrations have been organised by Moscow as a pretext to invade. Donestsk is one of the most industrialised parts of Ukraine, producing coal, steel, chemicals and turbines for nuclear plants.
It is also the home city of Viktor Yanukovich, the pro-Russian president who was toppled in Kiev 10 days ago. Most people in the region are ethnic Ukrainians who speak Russian as their first language. Few now support Yanukovich, though many still look to Russia as an ally.
Pro-Russian demonstrations have been held in several eastern and southern cities since Saturday, in some cases ending with Russian flags raised at regional government buildings.
Kiev says Moscow has organised the demonstrations and sent hundreds of Russian citizens across the frontier to stage them.
A protest in the eastern city of Kharkiv turned bloody on Saturday, with scores of people hurt in clashes when pro-Moscow demonstrators wielding chains and axe handles stormed the regional government building. Kharkiv was quiet on Monday.
(Writing by Peter Graff; editing by Timothy Heritage and Philippa Fletcher)