Ukrainian President Petro Poroshenko (left) met Arkady Babchenko on Wednesday: Reuters
The authorities in Ukraine have been sharply criticised for faking the murder of a Russian dissident journalist in Kiev.
An official from the Organization for Security and Co-operation in Europe (OSCE) said Ukraine was spreading "false information".
Reporters Without Borders said it was "part of an information war".
Ukraine said it had acted to foil a Russian plot to kill Arkady Babchenko. Moscow said it was a provocation, reports BBC.
Babchenko, a 41-year-old critic of the Kremlin, sent shock waves around the news world when he arrived at a press conference in Kiev on Wednesday - the day after he was reported dead.
The head of Ukraine's security service, Vasyl Hrytsak, said an elaborate sting operation had been set up to catch hitmen paid by Russian forces. Police reported making one arrest.
Relations between Kiev and Moscow have been tense since Moscow annexed Crimea in 2014 and was accused of covertly backing rebels in the bloody conflict in eastern Ukraine.