The Security Service of Ukraine (SBU) has launched criminal proceedings against 53 Russian citizens, mostly on terror charges, Chief of the SBU Main Investigation Department Vasyl Vovk has said.

"A total of 53 Russian citizens are subject to criminal prosecution... 47 of them on charges of committing terrorist attacks and illegal possession of weapons. Six more Russian citizens are suspected of espionage," Vovk said at a briefing in Kyiv on Wednesday.