Russian prison authorities said Navalny, 47, collapsed in the Harb penal colony in northwestern Siberia, adding that he “felt unwell” after a walk.
Navalny's health has deteriorated over the years as his role as Putin's chief rival has grown. He has been physically attacked, arrested, harassed, and in 2020 was poisoned with a Soviet-era nerve agent in an alleged assassination attempt.
The attack nearly cost him his life, and he has fallen ill numerous times over the past three years while in prison.
At well over six feet tall, Navalny was once a towering figure. However, while campaigning against corruption, he suffered a violent attack that left him with persistent health problems.
In 2017, shortly after his team released a video accusing then-Prime Minister Dmitry Medvedev of corruption, unidentified assailants threw green disinfectant in his face in public. The attack damaged his right eye, requiring surgery.
The most serious attack was nerve agent poisoning. He was on a flight departing from the city of Tomsk, where he was meeting with local activists, and fell seriously ill on the plane. In a video taken by another passenger and posted online, Navalny can be heard screaming in pain.
The plane made an emergency landing in the Siberian city of Omsk, and Navalny fell into a coma. He was eventually taken to Berlin for treatment, where German authorities announced he had been poisoned with the chemical nerve agent Novichok.
German Chancellor Angela Merkel rejected Russia's claims that poisoning could be ruled out, saying a military hospital had found “clear” evidence of operatives and declared Navalny a “victim of a crime”. said.
Novichok is a type of chemical weapon developed by the Soviet Union. It interferes with communication between muscles and nerves and blocks enzymes that the nervous system needs to function. This type of poison can be fatal and usually causes respiratory failure.
Navalny spent five months recuperating in Germany, relearning how to walk, talk and eat.
Robert Chilcott, a toxicology expert at the University of Hertfordshire in the UK, said there were not enough known cases of Novichok poisoning to say what the long-term health effects would be. That's what it means.
But perhaps there are similarities with “classic” nerve gases Chilcott said chemicals such as sarin can cause cognitive impairment, damage to nerves outside the brain and spinal cord, and changes in the immune system.
“It is certainly possible that previous exposure to Novichok contributed to the infection. [Navalny’s] A premature death,” Chilcott wrote in an email. “The circumstances of his incarceration certainly would have been an aggravating factor.”
Navalny returned to Russia in 2021, but was arrested shortly after landing at Moscow's Sheremetyevo International Airport on suspicion of violating parole in the previous incident.
Navalny was imprisoned until his death, first in a detention center and then in Penal Colony 2, about 110 miles east of Moscow. There, guards deliberately awoke Navalny and other prisoners in acts that amounted to torture, his lawyer Vadim Kobzev said. he said at the time.
Navalny said in a social media post at the time that he was experiencing numbness in his right leg and that a prison doctor gave him ibuprofen, but no diagnosis was made. He then went on a three-week hunger strike to protest his treatment at the facility, only to end when a civilian doctor warned him he might die.
Navalny continued to suffer from severe acute pain in his stomach and began having seizures, his lawyer and colleagues revealed last year.
Early last year, he developed a cough and fever, and his wife, Yulia Navalnaya, publicly appealed to prison authorities to provide him with medicine. At the same time, more than 200 Russian doctors signed a letter calling on President Vladimir Putin to “stop the abuse”, saying Navalny's health was “deliberately harmed”.
By the time of his death, he had been in solitary confinement for 300 days on suspicion of violations, which added to the stress on his system, his officials said. In April, he lost 17 pounds after just one stretch in his cramped cell, where he was only allowed a book and a glass.
“The blatant and highly bizarre circumstances surrounding Mr. Navalny's health, including seizures for which there were no previous symptoms, rule out the possibility that he is simply being 'slowly poisoned.' ”Kobzev posted on social media in April.
“This may sound paranoid and paranoid to others, but not to Mr. Navalny post-Novichok,” he said.
In August, a closed court convicted Navalny on multiple charges of financing and inciting “extremist” activities and sentenced him to 19 years in a “special regime” penal colony., The highest security prison in the Russian system.
Family visits are prohibited in the colony, a “special regime” reserved for the most serious criminals, and the lights in prison cells are kept on at all times.
In a social media post after the verdict, Navalny said he understood it was a life sentence. “I fully understand that, like many political prisoners, I am serving a life sentence. My life is about to be measured by my longevity or the longevity of this regime,” he wrote.
In December, Navalny's team lost contact with him for several weeks until he was transferred to a new regime, but eventually found him at Harp, also known as IK-3.
Halp Prison, which dates back to the Soviet-era concentration camp system, is geographically isolated and located in an area known for its harsh weather.
Russian prisons have long been criticized by human rights groups for widespread abuse, poor conditions and a lack of medical support. In its 2022 report on human rights in Russia, the State Department said there were reports that prison authorities systematically tortured inmates, “in some cases leading to death or suicide.”