A plane carrying Russian opposition leader Alexei Navalny took off from the Omsk on Saturday and landed in Germany for treatment of suspected poisoning, that has left him in a coma. The plane, chartered by the German NGO Cinema for Peace, took off around 8:00 am local time (0200 GMT) and touched down at 8:47 am local time (0847 GMT) at Tegel airport in Berlin, AFP reported.

The 44-year-old lawyer and anti-corruption campaigner, one of President Vladimir Putin’s fiercest critics, fell into a coma after becoming suddenly ill on Thursday on a plane to Moscow from Tomsk, that had to make an emergency landing in the Siberian city of Omsk.

His aides say they believe he was poisoned, apparently by a cup of tea at the airport, though Russian doctors said tests showed no trace of any poison. Doctors treating him in Omsk initially refused to let Navalny leave but reversed course after his family and staff demanded he to be allowed to travel to Germany.

Navalny’s spokeswoman Kira Yarmysh posted a picture on Twitter of him being lifted into the plane on a covered stretcher and said his wife Yulia was with him. An ambulance was earlier seen taking Navalny from the hospital after masked medics lifted a stretcher carrying Navalny into the ambulance.

Doctors at a Omsk hospital said he was in a coma and was on a ventilator support. Russian doctors have said tests did not find any trace of poison and said Navalny appeared to have a “metabolic disorder” and to have suffered a sharp drop in blood sugar levels.

The air ambulance arrived in Omsk on Friday morning but Russian doctors initially said that Navalny was too “unstable” to be moved. They announced on Friday evening that they had agreed to let him be transferred after German doctors examined him and the Cinema for Peace foundation said they were “willing and able” to transport him to Berlin.

The turnaround also followed a letter from Navalny’s wife Yulia with a direct appeal to Putin and after aides asked the European Court of Human Rights to intervene with the Russian government.

Navalny is the latest in a long line of Kremlin critics who have fallen seriously ill or died in apparent poisonings.

The air ambulance was dispatched to take Navalny to Berlin after Chancellor Angela Merkel extended an offer of treatment. European Union leaders including Merkel and French President Emmanuel Macron have voiced concern for Navalny, who has faced repeated physical attacks and prosecutions in more than a decade of opposition to Russian authorities.

Navalny lost consciousness shortly after his plane took off on Thursday from Tomsk in Siberia, where he was working to support opposition candidates ahead of regional elections next month. Yarmysh said he had seemed “absolutely fine” before boarding the flight and had only consumed a cup of tea at the airport.

She said she was sure he had suffered from an “intentional poisoning” and blamed Putin. She also claimed Russia’s refusal to evacuate Navalny was a ploy to “play for time” and make it impossible to trace poison, posing a “critical threat to his life”.