A medical evacuation plane carrying prominent Russian opposition figure Alexey Navalny landed in Germany from Siberia on Saturday, after the politician and anti-corruption activist fell gravely ill in a suspected poisoning.

Navalny has been in a coma in intensive care since Thursday.

The 44-year-old staunch critic of President Vladimir Putin fell ill on a flight back to Moscow from the Siberian city of Tomsk, his spokeswoman Kira Yarmysh said on Twitter. Yarmysh said Navalny drank tea that appeared to have been laced with a toxin.

Russian doctors say there is no evidence of poisoning, and the Kremlin denied the authorities tried to prevent the transfer from happening. But Navalny was only allowed to leave Russia after more than 24 hours of wrangling over his condition and treatment.

“Alexey is taken to the medical aircraft. Yulia is with him,” Yarmysh wrote on Twitter. Yulia is Navalny’s wife. She was initially refused access to him.

On Friday, doctors at Omsk Ambulance Hospital No. 1, where the politician was being treated, remained tight-lipped about his diagnosis saying only that they were considering a variety of theories, including poisoning. Local health officials said they found no indication that Navalny had suffered from a heart attack, stroke or the coronavirus.

Navalny will now be treated by doctors in Berlin.

He is the effective face of political opposition to Putin and he has been in and out of jail for his activism against Russia’s longtime leader.

Last year, Navalny claimed he was poisoned while serving a short jail sentence. Doctors said he had a severe allergic reaction to an unknown substance. He was left partially blind in one eye after a pro-Putin activist attacked him with a chemical in 2017.

Navalny attempted to run against Putin in Russia’s 2018 presidential elections but was barred from participating over a fraud conviction he alleged was politically motivated.