The governor of Russia's Belgorod region said armed groups had tried to cut off a road leading to Ukraine, Interfax news agency reported.
"Armed men are roaming the area. There was an attempt to close off the road from Moscow to Crimea," Yevgeny Savchenko was quoted as saying about events on Saturday. "This is really troubling."
Pro-Russia activists recaptured administrative headquarters in the Ukrainian city of Donetsk and flew the Russian flag from its roof.
ITV News' Europe Correspondent describes the tense atmosphere surrounds a central government building in Donetsk .
New footage obtained by ITV News shows Russian troops firing warning shots as Ukrainian soldiers approached during a tense stand-off today.