The doctors, who treated Russian Opposition leader Alexei Navalny after he was admitted into their care in August, published clinical report of his Novichok poisoning on Wednesday.

Navalny has repeatedly said that his medical report is a proof of his attempted assassination, which President Vladimir Putin has denied several times.

In an article published in the medical journal The Lancet, doctors at Berlin’s Charite hospital detailed symptoms observed in Navalny during his treatment.

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They also provided information on his physical responses as infusions, CT scans and MRIs that were carried out at the time.

“Ascertaining the involvement of a Novichok agent and its biotransformation products, in this case, was only achieved several days after establishing the diagnosis of cholinesterase inhibitor poisoning and did not affect therapeutic decision,” the article read.

Navalny had been flown to Germany for treatment after he collapsed on a flight from Siberia to Moscow.

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Experts from several Western countries have determined that Navalny was poisoned by the Soviet-era nerve agent Novichok, something that only Russian authorities can administer.

The clinical details were revealed just two days after Navalny posted a video of an extraordinary conversation with an alleged Federal Security Service (FSB) agent, who said that agents placed the poison in his underpants in August.

The telephone conversation had been recorded in a sting by Navalny, who said he had impersonated an official in the Kremlin’s Security Council to get the FSB agent to admit to the poisoning.