Russian court filings showed that two court hearings for opposition politician Alexei Navalny, scheduled for Monday, have been postponed until January.

The Kremlin critic's allies say his lawyers have not seen him since December 6 and have expressed concern over the lack of information about where he is.

What do we know about Navalny's whereabouts?

Navalny's spokesperson Kira Yarmysh wrote on X, the platform formerly known as Twitter, that it was the 13th day without news since Navalny's lawyers last had access to him.

Lawyers for Navalny's Anti-Corruption Foundation filed requests with more than 200 detention centers over the weekend, Yarmysh said, but they were still awaiting responses.

Navalny had been preparing for an expected transfer to a "special regime" colony, the most severe grading in Russia's prison system.

Russia's prison service announced on Friday that he was in the process of being moved to another prison in a different part of the country.

Such transfers, in which authorities move prisoners across the vast country by rail, can take weeks.

The prison service stated only that Navalny was no longer in the Vladimir region, where the latest case — over complaints made by the 47-year-old about his treatment — is being heard.

The UN Special Rapporteur on Human Rights in Russia, Mariana Katzarova, said the failure to reveal where Navalny is was alarming.

"I am greatly concerned that the Russian authorities will not disclose Mr Navalny's whereabouts and well-being for such a prolonged period of time, which amounts to enforced disappearance," she said.

Worries about dissident's health

Katzarova said Navalny had been persistently ill-treated in detention and deprived of access to adequate medical care, damaging his health and putting his life at risk.

Even before he went missing, Navalny's supporters had expressed concern about his health.

A former lawyer who rose to prominence by ridiculing Russian President Vladimir Putin's elite and exposing corruption, he galvanized major protests in Russia before he was jailed in 2021.

Navalny was immediately arrested after he returned to Russia in 2021 from Germany, where he had been treated for a near-fatal poisoning. He and independent investigators say the poisoning was carried out by the Russian state.

A court last convicted Navalny in August on charges relating to extremist activity and sentenced him to an additional 19 years on top of more than 11 he was already serving. Earlier this month, he was charged with "vandalism."

His allies say he has been regularly sent to a solitary cofinement cell, having spent at least 266 days in one.

rc/msh (AFP, AP, dpa, Reuters)