Russian opposition leader Alexei Navalny has released a recording of a phone call he said he made to an alleged state security operative who revealed details of how the politician was supposedly poisoned.
Mr Navalny fell ill on August 20 during a domestic flight in Russia and was flown to Berlin while still in a coma for treatment two days later.
Labs in Germany, France and Sweden, and tests by the Organisation for the Prohibition of Chemical Weapons, established that he was exposed to a Soviet-era Novichok nerve agent.
Russian authorities have vehemently denied any involvement in the poisoning.
Last week, the investigative group Bellingcat released a report alleging that operatives from Russia’s FSB domestic security agency with “specialised training in chemical weapons, chemistry and medicine” were “in the vicinity” of Mr Navalny in the time frame “during which he was poisoned”.
The investigation, conducted by Bellingcat and Russian news outlet The Insider in co-operation with CNN and German news outlet Der Spiegel, identified the supposed FSB operatives after analysing telephone metadata and flight information.
Mr Navalny, who is convalescing in Germany, said the report proved beyond doubt that FSB operatives tried to kill him on the orders of Russian President Vladimir Putin.
Mr Navalny is one of Mr Putin’s most strident critics.
On Monday, Mr Navalny posted a video on his YouTube channel titled “I called my killer. He confessed”.
The video showed him speaking on the phone with one of the alleged operatives.
One of the men, named by Mr Navalny as an employee of Russia’s FSB security service, spoke to him for 49 minutes. He said he was part of the clean-up team, and pointed to Mr Navalny’s underwear as a place where the substance that poisoned the politician may have been planted.
The man indicated he was involved in “processing” Mr Navalny’s clothes so “there wouldn’t be any traces”. The clothes Mr Navalny was wearing when he was first hospitalised in Russia, and placed into a coma, have not been returned to him.
Bellingcat and other media outlets identified the man Mr Navalny said he spoke to as Konstantin Kudryavtsev, a trained chemical weapons specialist.
The Associated Press was not able to independently verify the identity of the man.
Russian authorities have not yet commented on the recording, which received more than 1.4 million views on YouTube within hours of being posted.
Earlier in December, Russian officials brushed off the investigation by Bellingcat and other media outlets.
Mr Putin claimed last week that the investigation relied on data provided by US spy agencies.
Its authors have denied any link to US or any other Western intelligence services.
“It’s not some kind of investigation, it’s just the legalisation of materials provided by US special services,” the Russian leader said during his annual press conference.
He said Mr Navalny was not important enough for Russia to target him.
“Who needs him?”” he said. “If someone had wanted to poison him they would have finished him off.”