There was evidence that Russia's security service assisted their Ukrainian counterparts' attempts to suppress anti-government protests that culminated in bloodshed in February that left more than 100 people died, according to a top security official who spoke at the presentation of an official report in Kiev.
Prosecutor General Oleh Makhnitsky also said 12 members of an elite riot police unit have been held on suspicion of shooting protesters.
Mr Yanukovych fled Kiev after the culmination of the violence in February, precipitating the fall of his government.
The identity of the snipers believed to be responsible for most of the deaths has been the subject of disagreement. The interim government says Mr Yanukovych ordered snipers to be deployed - a charge he has denied.
Meanwhile, Russian Foreign Minister Sergey Lavrov has offered further assurances about a build-up of Russian troops on the border with Uktraine.
He said Russian troops "will be returning to the place of their permanent quarters as soon as other participants of the exercise have completed their tasks".
Mr Lavrov accused the Ukrainian government "and their patrons in the West of blowing this out of proportion".