BERLIN — Aleksei A. Navalny, Russia’s most prominent opposition leader, who was poisoned in August in Siberia, says he has no doubt that President Vladimir V. Putin was behind the attack.
In his first full interview since being released from the hospital, Mr. Navalny said that the use of a closely held, military-grade nerve agent in the attack was convincing evidence that it had been ordered at the highest level of Russia’s security or intelligence services.
“Putin is behind the crime,” he told the German newsmagazine Der Spiegel in an interview published on Thursday. “I have no other versions of the crime. I am not saying this to flatter myself, but on the basis of facts.”
Mr. Navalny has been recuperating in a Berlin hospital since he was flown to Germany after the poisoning. Although he became ill and collapsed on a domestic flight in Russia, he and his team believe that he was poisoned in his hotel room in the city of Tomsk, in Siberia. He was discharged from a German hospital last week after 32 days, many of them in a medically induced coma.
Initially, Mr. Navalny was treated for two days at a hospital in Omsk, Russia, where doctors offered a variety of diagnoses — none of them poisoning with a nerve agent from the Novichok family, as German military investigators determined — and claimed that he was too sick to be moved.
The opposition leader called that a ruse and said that the Russians had initially been determined not to let him leave the country.
“They were waiting for me to die,” he said.
While Moscow has maintained that it played no role in the poisoning, Mr. Navalny would not be the first Kremlin adversary to be attacked with Novichok. A former Russian spy, Sergei V. Skripal, and his daughter Yulia were poisoned by the same class of toxin in Salisbury, England, in 2018, touching off a crisis in relations between the countries.
Mr. Navalny said he hoped his recovery would be helpful in understanding the nerve agent.
“The Russian leadership has developed such an inclination to poison that it will not stop so soon,” he said. “My medical history will yet become instructive.”
The Novichok family of nerve agents was developed in the Soviet Union and Russia in the 1980s and ’90s, and can be delivered as a liquid, powder or aerosol. The chemical is said to be more lethal than other well-known nerve agents.
The poison causes muscle spasms that can stop the heart, cause fluid buildup in the lungs that can also be deadly, and damage other organs and nerve cells. Russia has produced several versions of Novichok, and it is anyone’s guess how often they have been used, experts say, because the resulting deaths can easily escape scrutiny, appearing like nothing more sinister than a fatal heart attack.
“The doctors say I can recover 90 percent, maybe even 100 percent, but nobody really knows,” Mr. Navalny told Der Spiegel. “Basically, I’m something of a guinea pig — there aren’t that many people you can watch living after being poisoned with a nerve agent.”
Mr. Navalny said he had long known that he could be subjected to arrest, beatings or even a targeted killing as a prominent opposition figure, but said he would never have suspected an attack with a chemical weapon like Novichok, since they are typically “reserved for secret service agents.”
“Nobody expected a nerve agent. I could hardly believe it myself. It’s like dropping a nuclear bomb on a person,” he said. “There are a million more effective methods.”
Mr. Navalny also described instantly suspecting that he had been poisoned when he began feeling ill on the flight, and lying down on the floor of the aircraft, convinced it was the end.
“I know that I am dead,” he said. “Only it turned out later that I was wrong.”
He also shed light on what his life has been like since being released from the hospital in Germany, and described his daily routine as “monotonous.”
“I train every day — otherwise I do nothing,” he said. “In the morning I walk in the park — that is my job — then I do exercises with the doctor. In the evening, I walk again. During the day, I try to work on the computer.”
Mr. Navalny said that he intended to return to Russia as soon as his health improves, because not returning would signal a victory for Mr. Putin. He also vowed to continue traveling throughout Russia and staying in hotels, despite fears for his life.
“They will use more sophisticated methods against us, and we will try to survive,” he said of himself and others who oppose Mr. Putin’s government.
When his interviewer noted that his hand was shaking as he poured a glass of water, he said the trembling was “not from fear,” but rather a result of the chemical agent.
“My task now is to remain the guy who is not afraid,” Mr. Navalny said. “And I am not afraid!”
Christopher F. Schuetzereported from Berlin and Megan Specia from London.