Russian police on Tuesday detained supporters of Alexei Navalny outside his penal colony east of Moscow after they were denied access to the jailed Kremlin critic, who is on hunger strike demanding proper medical treatment.

Among those detained was Anastasia Vasilyeva, Navalny's personal doctor and head of the Alliance of Doctors medical trade union which is critical of the government, according to the group and AFP journalists at the scene.

Her lawyer later said that she was returning to Moscow, although it was unclear whether she had been officially released.

Navalny's personal doctor Anastasia Vasilyeva wsa among those detained
Navalny's personal doctor Anastasia Vasilyeva wsa among those detained AFP / Kirill KUDRYAVTSEV

Meanwhile a CNN journalist was also detained before being released several hours later, he said on Twitter.

Police in the Vladimir region where Navalny's penal colony is located said in a statement that nine people were detained for violating "public order".

They said that around 45 people had gathered at the colony, including some 30 journalists and bloggers.

Police officers guarding the entrance to the penal colony
Police officers guarding the entrance to the penal colony AFP / Kirill KUDRYAVTSEV

Supporters of the 44-year-old opposition politician, including several doctors in white medical coats, arrived at the town of Pokrov around 100 kilometres (60 miles) east of Moscow earlier Tuesday to demand access to Navalny, but were rebuffed.

Navalny went on hunger strike last Wednesday to demand proper medical treatment for severe back pain and numbness in both legs, saying he had only been given painkillers.

On Monday, President Vladimir Putin's most vocal critic said he was now also suffering from a heavy cough and fever and that three people from his prison unit had been hospitalised with tuberculosis.

IMAGES Alexei Navalny's doctor Anastasia Vasilyeva arrives at a Pokrov prison where the Kremlin critic is detained and on hunger strike. Navalny, 44, announced the hunger strike last week, complaining a prison doctor had only given him painkillers as trea
IMAGES Alexei Navalny's doctor Anastasia Vasilyeva arrives at a Pokrov prison where the Kremlin critic is detained and on hunger strike. Navalny, 44, announced the hunger strike last week, complaining a prison doctor had only given him painkillers as treatment for severe back pain and numbness in his legs. AFPTV / Ekaterina ANISIMOVA

Later Monday, pro-Kremlin newspaper Izvestia cited the local branch of Russia's FSIN prison service in reporting that Navalny had been transferred to the colony infirmary and tested for the coronavirus. The FSIN declined to comment on Tuesday.

Navalny, who survived a near-fatal poisoning last August, has lost a total of 13 kilograms (28 pounds) in the penal colony, including five kilograms over the past week, his lawyer Olga Mikhailova said.

Navalny's doctor Vasilyeva accused authorities of violating his rights by refusing to treat him properly.

The protesters included several doctors in white coats who support Navalny
The protesters included several doctors in white coats who support Navalny AFP / Kirill KUDRYAVTSEV

"We are doctors -- that's why we are here today. Health should be a priority," she told reporters outside the penal colony, stressing that Navalny must be transferred to a "normal" hospital.

Later Tuesday the state-run TASS news agency cited Vasilyeva's lawyer Dmitry Dzhulay as saying that she was heading back to Moscow to ensure she does not violate her curfew restrictions on charges related to another protest.

Those charges were brought against her in January for allegedly violating restrictions related to the coronavirus pandemic by calling for people to join rallies in support of Navalny.

Also Tuesday Navalny's wife Yulia said in an Instagram post that she had received a letter from the head of the Pokrov colony saying that prison officials did not have the opposition figure's passport, meaning he could not be hospitalised or released early.

"Don't you forget, boss man, that if the unthinkable happens to Alexei, his death would be on Putin's conscience and yours, but Putin will throw you under the bus and make you a scapegoat," Navalnaya wrote, addressing the penal colony chief.

On Monday, the secretary general of Amnesty International, Agnes Callamard, said that she had written to Putin, urging him to make sure that Navalny is granted "immediate access to a medical doctor he trusts".

"There is a real prospect that Russia is subjecting him to a slow death," Callamard wrote on Twitter.

Putin's spokesman Dmitry Peskov on Tuesday said he was not aware of Callamard's letter, but added that Navalny was not entitled to any special treatment.

"Naturally, we cannot talk about any special conditions for one of the convicts," Peskov said.

Navalny was arrested in January after returning from Germany, where he spent months recovering from a poisoning attack he blames on the Kremlin.

On Monday, Navalny said that he would continue his hunger strike despite his deteriorating health.