Russian opposition leader Alexei Navalny on Tuesday said he was "fine" after a "pretty exhausting" 20-day transfer to a penal colony beyond the Arctic Circle.

Navalny's supporters said on Monday that the Kremlin critic, whose whereabouts had been unknown for more than two weeks, was now in the penal colony in Russia's far north and had been visited by his lawyer.

"Don't worry about me. I'm fine. I'm totally relieved that I've finally made it," Navalny wrote on X. 

"I'm still in a good mood, as befits a Santa Claus," he said, referring to his winter clothing and beard.

The US State Department said it remained "deeply concerned for Mr. Navalny's wellbeing and the conditions of his unjust detention".

Navalny mobilized huge anti-government protests before being jailed in 2021, after surviving an assassination attempt by poisoning.

He has spent most of his detention at the IK-6 penal colony in the Vladimir region, some 250 kilometers (155 miles) east of Moscow. 

A court in August extended his sentence to 19 years on extremism charges, and ruled he be moved to a harsher "special regime" prison that usually houses particularly dangerous prisoners.

The facility that Navalny is currently being held in is not a "special regime" one although there is one of that category in the same location.

One major difference from his previous place of detention is that any letters will take much longer to reach Navalny as they would go through the regular postal service rather than email.

Allies said his transfer could be linked to the upcoming presidential election in Russia, ahead of which many Kremlin critics have been jailed or fled.

Navalny posted on X that he arrived at the Arctic penal colony in the village of Kharp on Saturday and was visited by his lawyer on Monday.

Prisoner transfers in Russia can take weeks as inmates are moved by train to far-flung facilities in what was known as the Gulag in Soviet times.

"I didn't expect anyone to find me here before mid-January," he wrote, adding that he had seen little of his surroundings except for a snow-covered adjoining cell used as a yard and a fence outside his window.

"Unfortunately, there are no reindeer, but there are huge fluffy, and very beautiful shepherd dogs," he said.

Temperatures in Kharp are expected to go down to minus 26 degrees Celsius in the coming days.

bur/ach 

© Agence France-Presse