Russian dissident Alexei Navalny, who fell ill on a flight to Moscow in late August, has accused Russian President Vladimir Putin of orchestrating his assassination, the UK Guardian reported Thursday.

Navalny argued that only Putin could have authorized the use of the nerve agent novichok, a regular fixture of Russian political killings. German doctors found traces of novichok in Navalny’s system while treating him for his illness after the opposition leader’s team arranged for his departure from Russia.

Navalny, Russia’s foremost anti-Putin opposition figure, spent 32 days in Berlin’s Charite hospital after allegedly ingesting the Russian nerve agent on his flight from Tomsk to Moscow in August, the Associated Press (AP) reported. Russian doctors initially treated Navalny in a Siberian hospital and were hesitant to move him to Germany for better care, despite the urgings of European governments.

In his first interview since his release from the hospital, Navalny told the German newspaper Der Spiegel that Putin must have ordered his assassination, saying, “I assert that Putin was behind the crime, and I have no other explanation for what happened.”

Navalny said that only Putin could have given final approval for the use of novichok in any operation, insisting, “Only three people can give orders to put into action ‘active measures’ and use novichok. Those who know Russian states of affairs also know: FSB director Alexander Bortnikov, foreign intelligence service head Sergey Naryshkin and the director of GRU cannot make such a decision without Putin’s orders.”

Speaker of the Russian Duma Vyacheslav Volodin responded to the interview by claiming the poisoning was a Western intelligence operation and that Navalny had Putin to thank for his survival, according to the Guardian.

“Putin saved his life. If what happened to him was a specially directed operation by Western security services then this accusation fits with the logic. He was saved by everyone, from the pilots and doctors to the president,” he said.

The Kremlin vociferously denied Navalny’s accusations. Spokesperson Dmitry Peskov described them as “insulting and unacceptable.” He went on to accuse Navalny of cooperating with the American Central Intelligence Agency (CIA).

Novichok, a military-grade nerve agent, is believed to have been developed by Russia during the Cold War. It famously failed to kill former Russian intelligence agent Sergei Skripal in 2018 in another instance widely considered an attempted assassination by the Putin regime. The German government announced in early September it had obtained “unequivocal proof” that Navalny had ingested novichok, a claim the Russians denied.

Navalny’s chief of staff, Leonid Volkov, responded to the novichok announcement via Twitter, saying, “To poison Navalny with Novichok in 2020 would be exactly the same as leaving an autograph at a crime scene, like this one.” The image attached showed Vladimir Putin’s signature.

The Russian government claims third parties are able to replicate novichok and use it in “false-flag” operations with the aim of discrediting the Kremlin. Outside of Russia, the chemical agent was produced in a Soviet-era lab in Uzbekistan, but the government reached a deal to dismantle it with U.S. assistance in 1999, the New York Times reported.

Though initially unwilling to investigate the alleged poisoning, the Russian government announced in early September that Russian police were doing so, attempting to build a “timeline of events” leading up to Navalny’s flight; they still dismissed the German allegations of novichok poisoning.

The Russian government continues to deny any involvement in the incident. Last month, Peskov claimed the Navalny team’s story included “absurd inconsistencies” in the allegations surrounding the affair, specifically pointing to the absence of the bottle through which Navalny supposedly ingested the novichok.

“We cannot explain this, because this bottle, if it ever existed, had been taken somewhere in Germany or elsewhere. This means that an object that could serve as evidence of poisoning has been shipped away. This is yet another question: why and so on,” Peskov claimed.