Agnes Callamard, Secretary General of Amnesty International, accused Vladimir Putin Wednesday of subjecting Alexei Navalny to a slow death through torture and inhumane detention conditions.

Navalny, Putin’s most prominent critic, was poisoned in August 2020, the consequences of which Callamard alleges may be exacerbating his condition. Since his imprisonment earlier this year, reports indicate Navalny has been subjected to torture, such as sleep deprivation. Further, he claims not to have access to a doctor he can trust. Last week, he began a hunger strike because prison officials kept dismissing his complaints of pain in his back and legs. Since then he has been diagnosed with a double spinal hernia.

Many see Navalny’s arrest as politically motivated. After his August poisoning, he flew to Germany for medical care. Upon his return to Russia, officials arrested him, insisting he had violated his parole. Several years ago he was convicted of embezzlement, a charge also seen as politically motivated.

Since his arrest, the US and EU have imposed sanctions on Russian officials and entities. US President Joe Biden has joined other world leaders in calling for Navalny’s release.

Navalny’s continued detention could result in large protests. The “Free Navalny” website helps organize protests for his release, and nearly 400,000 have registered their intent to do so.