(Adds details, other protests)
KIEV, March 1 (Reuters) - Dozens of people were hurt in clashes on Saturday when pro-Russia activists stormed the regional government's headquarters in the eastern Ukrainian city of Kharkiv and raised the Russian flag, local media said.
The UNIAN news agency said thousands of people had gathered outside the building during a protest against the country's new leaders who ousted President Viktor Yanukovich a week ago.
The violence signalled that Ukraine's new leaders could face a challenge in mainly Russian-speaking regions that oppose the largely pro-Western course charted by the newly installed government.
The leaders of Crimea, a Black Sea peninsula with an ethnic Russian majority that is home to a Russian naval base, say they have joined forces with Russian servicemen to exert control over key buildings.
Russian parliament has approved a proposal by President Vladimir Putin to deploy troops in Ukraine.
Protests against the new authorities also took place on Saturday in other cities, including Odessa, Dnipro and Donetsk, Yanukovich's home town and power base.
The Russian flag was raised over the regional government building in Donetsk by several thousand pro-Russia activists waving the Russian tricolour and chanting "Russia! Russia!, witnesses said.
Donetsk authorities issued an appeal for a referendum to be called on the future status of the region. (Reporting by Pavel Polityuk, Editing by Timothy Heritage)