(Changes slug from UKRAINE-CRISIS/DONETSK-EVACUATION. Adds Gubarev quotes, details)
By Lina Kushch
DONETSK, Ukraine, March 5 (Reuters) - Ukraine ejected pro-Moscow demonstrators on Wednesday from a regional government building and raised its flag where Russia's had flown since the weekend, signalling an important shift of control in the Russian-speaking east.
The Donetsk administrative headquarters had been held since Monday by activists who burst in chanting "Putin come!" and demanded control over the regional police force and the end of ties with Kiev. Police said they evacuated it peacefully after receiving reports it was booby-trapped with explosives.
Donetsk, home city of deposed president Viktor Yanukovich, has seen the most persistent pro-Moscow demonstrations since protests erupted in eastern and southern cities on Saturday as Russian President Vladimir Putin declared his right to invade.
Russian forces have already seized control of the southern Crimea region but have not entered other parts of Ukraine. The main concern of Western officials meeting Russians in Brussels and Paris on Wednesday is Putin's threat of a wider invasion to protect Russian-speakers across Ukraine's industrial heartland.
By mid-day on Wednesday, Ukraine's blue and yellow flag had replaced the Russian tricolour atop the 11-storey building, but another Russian flag was still flying from a flagpole in front.
A large force of police was guarding the building with helmets and shields. Sniffer dogs had been brought to search it.
Around 200 pro-Moscow demonstrators were still clustered by tents in front of the building, where biscuits and tea were served from a cart. Their leader, burly local businessman Pavel Gubarev who has declared himself "people's governor", called the evacuation a "provocation" and vowed to re-enter the building.
"We are determined to erect our people's power in the Donetsk region. And we will not retreat. We have huge support," Gubarev said. "When we go back in, I don't want to see a single police officer in the building. Then we will go to the police, remove the boss that was imposed from Kiev, put our own boss in place and declare the police a municipal force."
Kiev accuses Moscow of organising the marches to create an excuse for military intervention, busing Russians across the border to protest. Some of Gubarev's followers are clearly outsiders who speak Russian without the distinctive local accent, although others appear to be from the area.
Pro-Moscow protesters raised Russian flags at government buildings in several eastern and southern cities on Saturday hours before Russia's parliament voted to give Putin the authority to invade. Others were quickly taken down, but the flag in Donetsk stayed up, and Gubarev and his followers burst into the building two days later.
"I AM RUSSIAN. DON'T PROTECT ME"
Russian troops have firm control of Crimea, an isolated Black Sea peninsula. Demonstrations in eastern and southern cities led to international concern over a wider operation.
Ukraine says it did not move in to reclaim the building in Donetsk by force or crack down on pro-Russian demonstrators elsewhere, to avoid violence that might provoke a Russian military response. Authorities have also acknowledged questions about the loyalty of some security forces.
Most Ukrainians in the east and south of the country speak Russian as a native language. Many people are deeply suspicious of the new government in Kiev and some have supported the pro-Russian demonstrators.
However, the protests have also produced a backlash, especially after scores of people were injured in the city of Kharkiv by demonstrators wielding axe handles and chains who stormed and trashed the government building on Saturday.
On Tuesday evening around 1,500 demonstrators marched in Donetsk waving Ukrainian flags and opposing Russian military intervention, the first time that pro-Kiev protesters outnumbered pro-Russian demonstrators in the city. Some carried placards reading: "I am Russian. Don't protect me."
Both sides have scheduled large demonstrations for later on Wednesday in Donetsk and several other eastern cities, meaning the day could provide an important signal of public opinion.
Kiev's new government has named one of Ukraine's richest men, metal baron Sergei Taruta, as Donetsk regional governor, a sign that powerful oligarchs, many of whom once supported Yanukovich, are now behind the new authorities.
Taruta has yet to appear at the Donetsk government headquarters to take up the job. On Wednesday morning he was shown on television speaking by video link to the Kiev cabinet.
"Everything is fine. Everyone is in place," Taruta said. He asked for help quickly appointing new security chiefs because of "sabotage from the side of the security forces". (Writing by Peter Graff; editing by Anna Willard)