(Adds Gubarev arrest, Taruta comments)
By Lina Kushch
DONETSK, Ukraine, March 6 (Reuters) - Ukraine flew its flag over the government headquarters in the eastern city of Donetsk on Thursday and ejected pro-Moscow demonstrators that occupied it, ending a siege that Kiev had seen as part of a Russian plan to create a pretext to invade.
Police said they had taken more than 70 people into custody for questioning after clearing out the regional administration headquarters and another government building.
"The people who were removed from the building did not resist," Donetsk city police chief Maksim Kirindyasov said. "The building was cleared in a matter of a few minutes."
Later on Thursday, security service agents arrested the protest leader. Pavel Gubarev was led away from his apartment without a fight. The local businessman who called himself the "people's governor" had demanded control over the police and tried to persuade lawmakers to install him as regional boss while his men occupied their hall.
He was charged with seeking to damage "the territorial integrity and independence of the state".
The pro-Moscow protesters who had been occupying the building since Monday were first lured out on Wednesday by police who said there was a bomb scare, but fought their way back in after battling police throughout Wednesday.
The building had flown the Russian flag since Saturday, when President Vladimir Putin declared Russia's right to invade Ukraine.
Donetsk, home city of deposed president Viktor Yanukovich, has seen the most persistent pro-Moscow demonstrations in a wave of protests that erupted simultaneously across southern and eastern cities the day of Putin's announcement.
SIMILARITIES TO CRIMEA
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.
On Thursday, Taruta promised to restore calm: "I am not a magician, I can't do it all in a single day, but I think in two weeks or so the situation will be completely different."
Russian forces seized Ukraine's Crimea region, an isolated Black Sea peninsula, but did not enter other areas of Ukraine.
Kiev says the protests across the south and east were orchestrated by Moscow to justify a planned wider invasion.
It points to similarities between Gubarev's tactics and those used in Crimea - where a pro-Russian politician was named provincial boss in a besieged legislature before Russian forces took control - as evidence a wider assault was planned.
The pattern was also repeated in other cities on Saturday where demonstrators raised Russian flags at regional government buildings and pro-Russian politicians held closed-door legislative sessions.
But Donetsk was the only city outside Crimea where the Russian flag flew above the government building for more than a day and the protest leader continued to insist he was in charge.
Most Ukrainians in eastern and southern regions speak Russian as a native language and many are deeply suspicious of the government in Kiev.
The pro-Moscow demonstrators initially enjoyed substantial support, but their tactics and Putin's invasion threat have increasingly caused a backlash and protest numbers have ebbed.
In Donetsk, anti-Russian protests in the past two days were much larger than the pro-Kremlin demonstrations.
Kiev has said that many of the pro-Russian demonstrators have been bussed in from Russia. Police chief Kirindyasov said those detained at the regional headquarters were all Ukrainian citizens from the Donetsk region, though not from the city itself.
The Ukrainian authorities say they did not take steps earlier against the pro-Moscow protests because of fear that violence would provoke a Russian military response. (Writing by Peter Graff; editing by Anna Willard and Giles Elgood)