The Kremlin has dismissed accusations that President Vladimir Putin sanctioned the poisoning of critic Alexei Navalny.
Spokesman Dmitry Peskov said the allegations were untrue and could not be taken seriously, reports the BBC.
Doctors in Germany, where Navalny is being treated, said he had "probably" been poisoned but Peskov questioned why they had "rushed" to that opinion.
Navalny fell ill on a flight from Tomsk to Moscow last Thursday.
His supporters suspect poison was placed in a cup of tea at Tomsk airport.
The flight of the arch-Putin critic was diverted to Omsk, where doctors treated him for three days before he was transferred to the Charité hospital in Berlin.
His condition is serious but not life-threatening, the Berlin doctors say.
Navalny, 44, made his name by exposing official corruption, labelling Putin's United Russia as "the party of crooks and thieves". He has served several jail terms which he says were the result of politically motivated charges.
There have been a number of previous attacks on high-profile critics or opponents of President Putin, including politicians, intelligence officers and journalists. The Kremlin has always denied involvement.