BERLIN — Doctors treating Aleksei A. Navalny, the prominent Russian dissident who fell ill while on a flight to Moscow last week, say tests indicate he was poisoned, but his life is not in danger, the Berlin hospital where he was admitted said in a statement on Monday.
Doctors at the Charité hospital in Berlin, where Mr. Navalny was taken on Saturday after his family and supporters pushed strongly for him to be treated abroad, said that their findings indicated intoxication by a substance from a group known as cholinesterase inhibitors.
“The specific substance has not been identified so far, and a further wide-ranging analysis has been initiated,” the doctors said, adding that the effect of the toxin “has been proven several times and in independent laboratories,” the statement said.
Mr. Navalny, who challenged President Vladimir V. Putin of Russia in the 2018 election, has been attacked at least twice before, including one assault that left him mostly blind in one eye. On Monday, he remained in an induced coma in stable condition.
The doctors said that although it was too early to tell what lasting effects Mr. Navalny would experience, “the possibility of long-term effects, particularly those affecting the nervous system, cannot be excluded.”
He was taken to Berlin on Saturday, more than 48 hours after he fell ill and his flight to Moscow was forced to make an emergency landing in Omsk, Siberia. His family and supporters organized an air ambulance to bring him to Germany, where Chancellor Angela Merkel had offered him access to medical care.
Ms. Merkel’s government enjoys strong economic and cultural ties to Russia but has not shied from criticizing policies of Mr. Putin, and even before Mr. Navalny arrived in Berlin, the German government appeared to be taking extra precautions to ensure his safety.
Minutes before landing, his plane was rerouted from Schönefeld Airport to Tegel Airport, and the ambulance that brought him from the tarmac to the Charité hospital was escorted by the police. A police van and several officers have been stationed outside the hospital’s main entrance since Saturday.
“It was clear that after he arrived here, security measures had to be put in place,” Ms. Merkel’s spokesman, Steffen Seibert, told reporters on Monday, before the hospital released its statement. “We are dealing with a patient who appears, with a certain level of probability, to have been the target of a poisoning attack.”
“Unfortunately there a one or more examples of such poisonings in recent Russian history,” Mr. Seibert added.
The Russian security services are suspected of having used a range of poisons to eliminate opponents, although Russian officials have consistently denied any evidence of poisoning. On Monday, doctors in Omsk who treated Mr. Navalny last week again denied that they had found any evidence of toxins in his system.