A police station and a state security building in eastern Ukraine were seized Saturday by armed men dressed in camouflage fatigues, an official said.
The two incidents took place in Sloviansk, a town about 100 km north of regional capital Donetsk near the Russian border, Xinhua reported.
The armed men initially occupied the police station, where they seized at least 400 handguns and 20 automatic weapons, Ukraine police said in a statement.
"The aim of occupying the police station was the guns which they are giving out the protesters in Sloviansk," the statement said.
The attack on the police station was followed by the storming of the state security building.
Ukrainian Interior Minister Arsen Avakov said on his Facebook page that the attack was led by "armed men in camouflage fatigues" and he vowed a severe response.
Ukrainian special forces had been dispatched to the scene, Avakov said, adding there was zero tolerance for armed terrorists.
Casualties and hostages remain unknown.
Earlier this month, pro-Russian protesters took over government buildings throughout eastern Ukraine.
After seizing government buildings in Ukraine's eastern city of Donetsk, the protesters proclaimed the region's independence from Kiev last week.
Russia has refused to take responsibility for the protests in eastern Ukraine.
