MOSCOW — Gravely ill Kremlin critic Alexei Navalny was flown out to Germany for treatment early Saturday, ending a standoff between doctors and Navalny allies who accuse Russian officials of attempting to cover up a suspected poisoning of the country's most prominent opposition leader.

The decision to allow Navalny to leave a Siberian hospital to be transferred to one in Berlin followed conflicting accounts on his condition and whether the comatose Navalny could be taken aboard a German plane that was sent to Omsk.

Alexander Murakhovsky, chief physician at Omsk Emergency Hospital No. 1, said Friday that Navalny could be transferred to German care. Earlier in the day, he said the 44-year-old Navalny was not well enough to be moved.

Murakhovsky added that there was no indication Navalny was poisoned, though he earlier said it would take two days for test results.

The confusion added to the many questions since Navalny fell into a coma Thursday after he became suddenly ill on a flight en route to Moscow from Siberia. His spokeswoman and others quickly claimed that Navalny was the latest victim of a poisoning ordered by the state, a method used before in attacks linked to Russian agents.

Doctors treating Navalny said his condition had improved but gave few other details.

Navalny left Saturday on a German ambulance aircraft, dispatched by Berlin-based human rights activist Jaka Bizilj's Cinema for Peace Foundation. The plane arrived in Omsk on Friday, along with three German physicians who were later allowed to examine Navalny.

But Navalny's associates wrote on Twitter that the doctors were spirited away by unidentified authorities before they could share their conclusions with Navalny's wife, Yulia Navalnaya. She said in a video that she was blocked from trying to speak with the Germans at the hospital.

Navalny's spokeswoman, Kira Yarmysh, earlier accused the Russian physicians of endangering Navalny's life, suggesting on Twitter that they wanted to hinder an investigation by stalling "until the poison in his body can no longer be traced."

“The ban on transporting Navalny is an attempt on his life, which is now being carried out by the doctors and the deceitful authorities who sanctioned it,” she said. Less than four hours after German doctors reportedly said it was safe for Navalny to travel, the Omsk hospital gave the clearance for Navalny to be moved.

Navalny’s plight has become a rallying point for Russian opposition groups and others who charge that President Vladimir Putin’s regime was responsible for the alleged toxic attack. The initial decision to block his release fueled anger over perceived interference from the Kremlin.

Navalny’s wife personally appealed to Putin in a letter to allow Navalny to be transported to Germany.

Murakhovsky, the chief physician at the Omsk hospital, said Friday morning that doctors have “five working diagnoses” but that he could not offer details. He later said that the most likely cause for Navalny’s coma is “a metabolic disorder, caused by a sharp drop in blood sugar levels during the flight.”

Russian opposition leader Alexei Navalny was in a coma on Aug. 20, after drinking a cup of tea that his spokeswoman believes was laced with poison. (Reuters)

Meanwhile, Ivan Zhdanov, a Navalny associate, said Friday that transportation police told him they discovered poison they deemed dangerous not only for Navalny but also for those around him — so much so that access to Navalny will not be permitted without visitors wearing full hazmat suits. Zhdanov said the authorities did not disclose details of the poison, citing an active investigation.

Omsk physicians later said that the transportation police were referring to an industrial chemical substance that was found not in Navalny’s blood but on his clothes. They added that it did not poison Navalny. Multiple calls to the transportation police department were not answered.

The Russian state news agency Tass, citing an anonymous law enforcement source, reported that a criminal investigation has not been opened, because there is no evidence yet that points to intentional poisoning. Photos posted to social media by Navalny’s aides have shown a heavy police presence at the hospital.

Navalny, who once described Putin’s ruling party as one “of crooks and thieves,” has no shortage of powerful enemies in Russia. In addition to his criticism of the government, Navalny’s Anti-Corruption Foundation exposed excesses and alleged corruption by members of Russia’s elite who are enriched through Kremlin connections.

His possible poisoning is reminiscent of other high-profile toxic attacks against outspoken Russians. In those instances, the victims were either already abroad and received subsequent treatment outside Russia or, as with Navalny, their families requested urgent evacuation.

In 2006, Alexander Litvinenko, a former spy and dissident, died of polonium-210 poisoning in London after accusing Putin from his hospital bed of being responsible for the attack. Two years ago, Sergei Skripal, a former double agent, and his adult daughter, Yulia Skripal, were poisoned in the British city of Salisbury after they came into contact with a deadly Soviet-era nerve agent known as Novichok.

In 2015, opposition activist Vladimir Kara-Murza suffered kidney failure from a suspected poisoning in Moscow. He eventually recuperated in the United States. In a second alleged poisoning two years later, samples of Kara-Murza’s blood, hair and fingernails were sent to laboratories in France and Israel in an effort to identify the toxin, but there were no conclusive findings on whether he was intentionally poisoned.

Pyotr Verzilov, a member of Russian protest group Pussy Riot, ended up in a Moscow intensive care unit after a suspected poisoning in 2018 and was then flown to Berlin for treatment, but experts could not determine the cause. He had been working with officials in Germany to arrange the same for Navalny.

“The Kremlin and the Ministry of Health will now do everything possible to prevent the evacuation of Alexei,” Verzilov said Friday on Twitter. “The details of Navalny’s poisoning must remain in Russia.”

William Glucroft in Berlin contributed to this report.