The Russian opposition leader’s health has been a constant source of concern during his time in prison. Volkov expressed concern over Navalny’s condition and ability to continue communicating now that he’s in solitary.

“Now the situation is, I have to admit, very bad, because now his communication with the outside world is very limited, and his health is endangered and his physical condition might get worse,” Volkov said. “We have to keep talking about Navalny,” he added.

Navalny, who is Putin’s most prominent critic, was poisoned with a Soviet-era nerve agent in Siberia in August 2020. Putin has been widely blamed for the incident, which nearly killed Navalny. The Russian leader has denied any involvement.

After receiving treatment in Germany for several months following the poisoning, Navalny returned to Moscow in early 2021 and was promptly arrested. The Russian opposition leader was thrown behind bars on charges condemned across the world as politically motivated and has since seem time tacked on to his sentence.

Navalny’s imprisonment led to mass protests in 2021. Last June, Volkov told Insider that Putin was “dumb” to throw Navalny in prison because it turned the anti-corruption campaigner into a symbol for Russians to rally behind.

John Haltiwanger is a Political Correspondent at Business Insider. He reports on all things politics with a focus on national security and foreign policy. John has a BA in History from St. Mary’s College of Maryland and an MSc in International Relations from the University of Glasgow. When he’s not reporting, John is likely searching for the best pizza slice in Brooklyn or watching/playing soccer. This first appeared in Insider.