Kremlin critic Alexei Navalny says he had tricked a Russian secret agent into disclosing details of the botched plot to kill him and had been told that poison had been placed in his underpants.

Before a joint media investigation was released, identifying an FSB-run team of assassins whose attempt on Vladimir Putin critic Alexei Navalny was recently botched, the victim of novichok poisoning decided to call one of the alleged members of the toxins squad, posing as an aide to the country's security council seeking individual reports on the reasons why the whole operation failed.

Navalny says one of the men, who he says works for Russia’s FSB and appears to have been part of the clean-up team, talked to him for 49 minutes, exposing details of the botched mission, Reuters reports.

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The Kremlin has repeatedly rejected any suggestion that Russia tried to kill Navalny, dismissing the latest prank call as "fake" and a planned provocation.

In the video published by Navalny, when asked why their target survived, the voice allegedly belonging to the operative in question, Konstantin Kudryavtsev, says it was probably because the plane he was on at the time made an emergency landing and he was treated professionally and quickly by Russian medics.

"If it had been a bit longer, then it's possible it would all ... have ended differently," the voice says.

Labs in Germany, France and Sweden, and the Organization for the Prohibition of Chemical Weapons, established that Navalny was exposed to a variant of the novichok nerve agent, the other modification of which was used in Salisbury in an assassination attempt targeting a Russian spy turncoat Sergei Skripal, whose daughter was also affected in the poisoning attack.

Read alsoNavalny poisoned by FSB elite unit's operatives: Media reveal namesKonstantin Kudryavtsev stated that the highest concentrations of toxic residue could be found on Navalny’s clothes, particularly in "the inside of Navalny’s underpants" and "the seams in the crotch area," according to Deutsche Welle.

Navalny poisoning: Background

Russian opposition leader Alexei Navalny felt sick on board the plane he was flying from the city of Tomsk to Moscow on August 20. His rapidly deteriorating condition forced the captain to perform an emergency landing in Omsk.

Navalny was evacuated from Omsk to Berlin's Charite hospital on an ambulance aircraft for further medical treatment on August 22.

On September 4, it was announced that experts with the Bundeswehr laboratory had found traces of poison from the Novichok group in Navalny's body. In this regard, Berlin called on Moscow to explain the circumstances of the poisoning of the Russian opposition figure.

On September 10, it was reported Navalny had made further progress in his recovery and was able to speak again.

On September 14, French and Swedish laboratories independently confirmed Navalny had been poisoned with a chemical nerve agent of the Novichok group.

On September 23, he was discharged from Charite. He is now convalescing in a secret location.

Read alsoFive countries' envoys to UN call on Russia to disclose circumstances of Navalny's poisoningOn September 25, Navalny's press secretary, Kira Yarmysh, said that the opposition leader would remain in Germany until the end of his rehabilitation course.

On October 1, speaking in an interview for Germany's Der Spiegel, Navalny said that Russian President Vladimir Putin was personally behind the attempt to poison him with Novichok. Navalny said he planned to return to Russia.