Pro-Kremlin media on Friday launched an offensive against jailed Kremlin critic Alexei Navalny aiming to disprove his complaints of mistreatment and lack of medical attention at his penal colony.

On Wednesday, 44-year-old Navalny announced he had launched a hunger strike demanding proper medical treatment in prison after experiencing severe back pain and numbness in his legs.

The opposition figure is serving a 2.5-year sentence on old fraud charges in a penal colony some 100 kilometres (62 miles) east of Moscow known for its harsh discipline.

The pro-Kremlin news website on Friday published CCTV footage from what it said is Navalny's penal colony.

Several videos showing what looks like a prison dormitory show a man strongly resembling Navalny, dressed in a dark blue uniform with a shaven head.

The videos are dated March 26, just under two weeks after he was transferred to Penal Colony No. 2 outside the town of Pokrov and a day after he publicly said his health was deteriorating.

Describing Navalny as an "impudent simulator", wrote that he was walking around and was disrespectful to prison authorities, although the published videos have no sound.

The website did not say how it obtained the footage.

Kremlin critic Alexei Navalny is being held in one of Russia's most notorious prison camps
Kremlin critic Alexei Navalny is being held in one of Russia's most notorious prison camps AFP / Dimitar DILKOFF

In posts on social media, Navalny has accused prison officials of "torture" through sleep deprivation and said he lost eight kilogrammes (18 pounds) since arriving at the colony and before going on hunger strike.

On Wednesday he said the Kremlin-funded broadcaster RT (formerly Russia Today) was filming at his colony.

He added that the crew was led by Maria Butina, who was convicted in the United States for illegally acting as an agent of a foreign government and served more than five months in a correctional facility before being deported back to Russia in October 2019.

Butina on Friday confirmed she was at the Pokrov colony in a post on her Telegram channel, saying Navalny "looks quite normal".

She said the colony is "practically exemplary" and "resembles a pioneer camp", referring to Soviet summer camps.

"My wish for Alexei is that if you have committed a crime, be a man and serve your time."

Navalny was arrested when he returned to Russia in January from Germany, where he had spent months recovering from a near-fatal poisoning he blames on the Kremlin.

Reached by AFP, Navalny's close ally Leonid Volkov said: "We do not comment on Kremlin infofeces."