A Ukrainian security service official said a recent explosion at a rock bar in Kharkiv that injured a dozen people was caused by a plastic explosive device and suggested a Russian-backed group were involved.
Last week's blast at the Stena (Wall) club in the the northeastern city of Kharkiv was caused by a device similar to one confiscated from an anti-government militant group last month, said Oleksandr Pyvovar, the head of the Kharkiv branch of Ukraine's Security Service, UNIAN reported.
The group, the Kharkiv partisans, had allegedly planned to stage a series of bombings in the run-up to the country's parliamentary election.
"We know that explosives of this kind were used even back in the Soviet time, and there are sill supplies of them in Russia," Pyvovar was quoted as saying.
The security service had previously claimed that Kharkiv Partisans were headed by a Russian citizen.
"We know the individuals who supplied [the explosives] and took part in the subsequent terrorist acts," Pyvovar was quoted as saying. "We know who we are looking for, we know who sent them, who inspired that crime."
The club where the blast occurred was renowned for its management's pro-Ukrainian stance and was popular among fighters returning from the conflict against pro-Moscow separatists in southeastern Ukraine, Ukrainian media reports have said.
Initial reports said that a gas leak was to blame, but the club owner blamed a bomb concealed inside a bag that he said customers had spotted shortly before the blast.