Alexei Navalny, Russian President Vladimir Putin’s loudest foe, has been keeping up a running commentary against the invasion of Ukraine and the man he calls the “insane tsar” — from behind bars in a maximum-security prison.

“The war was intended to cover up the robbery of Russian citizens and divert their attention away from the country’s internal problems, from the degradation of its economy,” Navalny posted to his Instagram account — which mysteriously continues to add messages and videos from the unbowed opposition leader.

“The war was unleashed by the Kremlin gang to make it easier for them to steal,” he wrote.

On Friday, Navalny, 45, spoke out against Putin’s invasion of Ukraine in a grainy video of a court proceeding recorded in the Pokrov maximum security prison, 60 miles east of Moscow, where he has been held for more than a year.

“I am against this war,” Navalny said in the clip, which has gained more than 2 million likes, the Sunday Times of London reported. “I find it immoral, fatal and criminal.”

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He has urged his 6.3 million social-media followers to “take to the streets and fight for peace. “You need to go out to anti-war rallies every weekend, even if it seems that everyone has either left or got scared,” he wrote this week. Even if you are alone … you are the backbone of the movement against war and death.”

Navalny, who survived an apparent poisoning in 2020, is being held on allegations that he misdirected funds from his Anti-Corruption Foundation for personal use — a charge that could keep him jailed for three decades.