Russian opposition leader Alexei Navalny, in coma, arrives in Berlin for treatment

Aug. 22 (UPI) -- An emergency medical plane carrying Russian opposition leader Alexei Navalny arrived in Germany on Saturday so he can receive treatment for a mysterious condition.

His transfer to Berlin's Charite hospital came after waffling by his doctors at Omsk Emergency Hospital No. 1 in Russia on Friday. They initially refused to allow him to be moved, insisting he was too unstable to travel.

They reversed their decision later in the day. Navalny was in a coma and "critical condition" when he arrived in Germany, the Washington Post reported.

Navalny, a fierce critic of Russian President Vladimir Putin, has been in an induced coma after taking ill Thursday while traveling from Tomsk to Moscow.

After landing at an airport in Tegel, the 44-year-old was rushed to the Berlin hospital by an ambulance accompanied by police vehicles, The Guardian reported. The hospital said it would provide an update on his condition after testing.

Navalny's spokeswoman, Kira Yarmysh, who was traveling with him when he became sick, said doctors believe he was poisoned but the chief physician in the Siberian hospital where he was first taken said they could find "no trace" of poison in his system so far, raising suspicion about the reluctance to transfer him to a facility in Germany.

Alexander Murakhovsky, chief of medicine at Omsk hospital, said Navalny's condition may be caused by a metabolic disorder.

"Today we have some working diagnoses. The main one we are arriving at is the disorder in the carbohydrate balance, that is, a metabolic disorder. It may have been caused by a sudden drop in blood sugar levels," he said.

Navalny is an anti-corruption activist and member of the Progress Party. He unsuccessfully ran for mayor of Moscow in 2013, president of Russia in 2018 and a member of the Duma in 2019.

He's been arrested multiple times, something his supporter believe is in retaliation for his opposition to Putin's regime.