Russia’s state media is reporting imprisoned opposition leader Alexei Navalny has died at age 47. Prison authorities said in a statement earlier today Navalny felt ill after going on a walk and lost consciousness. They say medical staff were unable to resuscitate him. The cause of death has not been determined. Navalny’s spokesperson Kira Yarmysh said on social media their team had not received confirmation of his death and that Navalny’s lawyer was traveling to the penal colony, located in the town of Kharp in the Arctic Circle, where Navalny was serving a 19-year sentence on charges of “extremism” over his criticism of Russian President Vladimir Putin. The prison, nicknamed “Polar Wolf,” is among the harshest in Russia, due in part to the severe winter.

Navalny had been detained since 2021, when he returned to Moscow after an assassination attempt with a nerve agent in 2020. Navalny has been hailed as an anti-corruption crusader who was willing to stand up to Putin, and has also been condemned for his past antisemitic and ultranationalist comments and actions.