An ally of Kremlin critic Alexei Navalny said on Thursday that a proper Russian investigation would show that President Vladimir Putin, the Kremlin and the security services were responsible for poisoning the politician.
The comments were made on YouTube by Georgy Alburov, a member of Navalny's team.
Laboratories in Germany, France and Sweden have established Navalny was poisoned by a Novichok nerve agent, a poison developed by the Soviet military, though Russia denies this and says it has seen no evidence.
The Kremlin has rejected any suggestion Putin or the Russian authorities were involved.