Navalny, a former lawyer who rose to prominence by lampooning President Vladimir Putin’s elite and alleging vast corruption, was sentenced in August to an additional 19 years in prison on top of the 11-1/2 years he was already serving.

Allies, who had been preparing for his expected transfer to a “special regime” colony, the harshest grade in Russia’s prison system, said Navalny has not been seen by his lawyers since Dec 6.

A Navalny lawyer, Vyacheslav Gimadi, said that prison officials told a court on today that Navalny had left the IK-6 facility in Melekhovo, 235km east of Moscow. They did not say where he was taken.

“Where he was taken is not known,” Navalny’s spokesman, Kira Yarmysh, said, adding that lawyers had been told that he left the Vladimir region where IK-6 is located on Dec 11.

“Let me remind you that the lawyers have not seen Alexei since Dec 6. Why they were not allowed to meet with him, if Alexei was still in IK-6, we do not know.”

Navalny earned admiration from Russia’s disparate opposition for voluntarily returning to Russia in 2021 from Germany, where he had been treated for what Western laboratory tests showed was an attempt to poison him with a nerve agent.

Navalny says he was poisoned in Siberia in August 2020. The Kremlin denied trying to kill him and said there was no evidence he was poisoned with a nerve agent.

His supporters cast him as a Russian version of South Africa’s Nelson Mandela who will one day walk free from jail to lead his country.

But Russian authorities view him and his supporters as extremists with links to the Central Intelligence Agency who are seeking to destabilise Russia. They have outlawed his movement, forcing many of his followers to flee abroad.

US state department spokesman Matthew Miller said on Monday that Washington was deeply concerned about Navalny’s well-being and had reminded the Russian authorities that they were responsible for what happened to him.

The Kremlin, which said it did not track the movements of individual prisoners, told Miller and his colleagues to mind their own business.

“Here we are talking about a prisoner who has been found guilty under the law and is serving his sentence. And here we consider any interference by anyone, including the US, as unacceptable and impossible,” Kremlin spokesman Dmitry Peskov told reporters this week.