* Armed men seize regional government, parliament buildings
* Police gather outside, Russian flag flying
* Door barricaded with chairs, tables
By Alessandra Prentice
SIMFEROPOL, Ukraine, Feb 27 (Reuters) - Armed men seized the regional government headquarters and parliament on Ukraine's Crimea peninsula on Thursday and raised the Russian flag.
A Reuters correspondent on the scene in the Crimean capital, Simferopol, said the door of the parliament was blockaded from inside by tables and chairs and no one was now able to enter.
Interfax news agency quoted a witness as saying there were about 60 people inside and that they had many weapons. It said no one had been hurt when the buildings were seized in the early hours of Thursday.
"I heard gunfire in the night, came down and saw lots of people going in. Some then left. I'm not sure how many are still in there," a 30-year-old man who gave his name only as Roman told Reuters.
Crimea, the only Ukrainian region with an ethnic Russian majority, is the last big bastion of opposition to the new political leadership in Kiev following the ouster of President Viktor Yanukovich on Saturday.
Ukraine's new leaders have been voicing alarm over signs of separatism there. The seizure of the building was confirmed by the country's acting interior minister, Ukrainian television said, but he gave few details.
Russian President Vladimir Putin has ignored calls by some ethnic Russians in Crimea to reclaim the territory handed to then Soviet Ukraine by Soviet Communist leader Nikita Khrushchev in 1954.
The United States says any Russian military action would be a grave mistake.
Ethnic Tatars who support Ukraine's new leaders and pro-Russia separatists had confronted each other outside the regional parliament on Wednesday.
A local Tatar leader, Refat Chubarov, said on Facebook: "I have been told that the buildings of parliament and the council of ministers have been occupied by armed men in uniforms that do not bear any recognisable insignia."
"They have not yet made any demands," he said.
About 100 police were gathered in front of the parliament building. Doors into the building appeared to have been blocked by wooden crates.
The streets around the parliament were mostly empty apart from people going to work.
Yanukovich was ousted after three months of unrest led by protesters in Kiev. He is now on the run being sought by the new authorities for murder in connection with the deaths of around 100 people during the conflict.
With a part of Russia's Black Sea fleet based in the port of Sevastopol, Crimea it is the only region of Ukraine where ethnic Russians dominate in numbers, although many ethnic Ukrainians in other eastern areas speak Russian as their first language.
The Tatars, a Turkic ethnic group, were victimised by Soviet dictator Josef Stalin in World War Two and deported en masse to Soviet Central Asia in 1944 on suspicion of collaborating with Nazi Germany.
Tens of thousands of them returned to their homeland after Ukraine gained independence with the collapse of the Soviet Union at the end of 1991.