Russian opposition leader Alexei Navalny is being flown to the Siberian city of Omsk for treatment in Germany.
He fell into a coma after drinking what his followers thought he was tea; they accuse the authorities of trying to conceal a crime.
Doctors treating him in Omsk insisted on Friday that he was too ill to move.
But they later said his condition was stable enough for the flight.
A medically equipped plane, paid for by the German NGO Cinema for Peace, flies Mr Navalny to Berlin, where he will be treated at the Charité hospital.
“Alexei Navalny is loaded into an ambulance and they are taking him to the airport,” his spokeswoman Kira Yarmysh tweeted early Saturday.
She said earlier that it was unfortunate that doctors took so long to approve his flight because the plane had been ready since Friday morning.
Mr Navalny fell ill on Thursday during a flight from Tomsk to Moscow, and his plane made an emergency landing in Omsk. A photo on social media is meant to show him drinking from a bag in a Tomsk airport cafe before the flight. His team suspected that a poisonous substance had been put in his tea.
Disturbing video appeared to show a stabbed Mr Navalny crying in pain during the flight. Passenger Pavel Lebedev said he heard the activist “writing in pain”.
What the doctors said Friday
The chief doctor at the hospital where Mr Navalny was treated in Omsk, Alexander Murakhovsky, warned late on Friday that they do not recommend flights, “but his wife insists that her husband be transferred to a German clinic”.
“The patient’s condition is stable,” Deputy Chief Physician Anatoly Kalinichenko was quoted as saying by the Interfax news agency.
Mr. Navalny is in an induced coma, and his condition is reported to be stable.
Russia’s worthy Putin critic
“Because we are in possession of a request from survivors to allow him to be transported somewhere, we have now decided that we will not object to his transfer to another institution for patients.”
Doctors previously said no toxin was found in his body, suggesting that his condition may be due to a “metabolic disorder” caused by low blood sugar.
Health officials then indicated that traces of an industrial chemical had been found on his skin and hair. The local Interior Ministry told the legal news agency Rapsi that the chemical was commonly incorporated into polymers to improve its elasticity, but its concentration was impossible to establish.
Leading critic of President Vladimir Putin has consistently exposed official corruption in Russia. He has served multiple prison sentences.
What do Mr Navalny’s supporters say?
At a news conference in Berlin, Mr Navalny’s assistant Leonid Volkov initially said that doctors at the hospital had helped facilitate his transfer, but abruptly stopped doing so.
“[It was] “as something was disabled – such as medicine mode disabled, cover-up surgery mode – and the doctors refused to cooperate more, refusing to provide any information, even to Alexei’s wife,” he said.
“The doctors who helped do the paperwork to make the transport from Alexei to Charité possible, began to say that he is no longer transportable, he is not more stable and contradicts himself.”
The Cinema for Peace Foundation was founded by activist and filmmaker Jaka Bizilj. In 2018, it ruled out the treatment of Pyotr Verzilov – an activist with the Russian protest group Pussy Riot – who had symptoms of poisoning.
Mr Verzilov’s ex-wife, activist Nadya Tolokonnikova, told BBC News that Mr Navalny’s condition was similar to the “poisoning” of her ex-husband.
“What German doctors told me after I found no poison in my ex-husband’s blood is that the poison disappears in three days. That the Russian doctors left him alone when they were sure there was no trace of poison left over, “she explained.
She also expressed surprise at what happened to Mr Navalny: “I thought Alexei was so powerful as a political figure that Mr Putin would not interfere.”
Navalny’s wife Yulia wrote to President Putin asking him to move her husband. She was afraid that the Russian authorities would stop so that evidence of any chemical substance would be lost.
The spokesman for Mr. Putin Dmitry Peskov said on Thursday that the Kremlin would help move Mr Navalny abroad if needed and wished him a “speedy recovery”. On Friday, he said it was purely a medical decision.
Foreign leaders including German Angela Merkel and France Emmanuel Macron have expressed their concern for Mr Navalny. In the US, Democratic presidential candidate Joe Biden described the incident as “unacceptable” and promised that if elected, he would “stand up for autocrats like Putin.”
Timeline: Navalny directed
April 2017: He was taken to hospital after an antiseptic green dye splashed on his face in Moscow. It was the second time he was that year with Zelyonka (“brilliant green” in English). “It looks funny, but it hurts like hell,” he tweeted after the attack.
July 2019: He was sentenced to 30 days in prison after asking for unauthorized protests. He fell ill in prison and doctors said he had suffered an acute allergic reaction, diagnosing him with “contact dermatitis”. His own doctor stated that he may have been exposed to “some toxic agent” and Mr Navalny said he thought he might have been poisoned.
December 2019: Russian security forces raided the offices of its Anti-Corruption Foundation, seizing laptops and other equipment. CCTV footage showed officials using power tools to get through the door. Earlier that year, his organization was declared a ‘foreign agent’.