DONETSK, Ukraine -- Anti-government demonstrators in one of eastern Ukraine's main cities have stormed the local prosecutor's office.

Riot police fired stun grenades as the protesters moved on the building in Donetsk on Thursday, but some demonstrators wrested shields away from officers. It wasn't immediately clear if protesters had entered the building.

The clash came after a march by several hundred people carrying flags of the Donetsk People's Republic, a movement that seeks either greater autonomy from the central government, or independence and possible annexation by Russia.

Donetsk is the heartland of support for Russia-friendly former President Viktor Yanukovych, who was ousted in February after months of protests in the capital. Opponents of the government that succeeded him have seized buildings in about a dozen cities and towns in eastern Ukraine.