Ukrainian forces clashed with pro-Russian separatists in Mariupol on Friday at the port town's police headquarters and at the local interior ministry building, killing eight people and wounding others, Interfax- Ukraine news agency reported.
The news agency said police were trying to wrest back control of the police building when they came under fire from pro-Russians who had taken the interior ministry building.
Local police in the eastern Donetsk region, centre of a pro-Russian rebellion against Kiev, said they could not comment.
Tetyana Ignatchenko, a journalist in Mariupol, said there was fierce fighting outside the police headquarters which pro-Russian rebels had seized. She said there was one dead and six wounded on the rebel side.
Ukrainian forces had brought had brought several armoured cars into the town, a major industrial and shipping centre with a population of about half a million.