Supporters of jailed Kremlin critic Alexei Navalny are raising deep concerns about his decision to launch a hunger strike, saying they fear more damage to his already-fragile health.
The 44-year-old is serving two-and-a-half years on old fraud charges in a penal colony east of Moscow. He 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.
Navalny says he is suffering in prison from severe back pain and numbness in his legs and has only been given painkillers.
His allies said his announcement of a hunger strike is no idle threat and they do not expect he will back down.
"Navalny has always taken such a step as a hunger strike extremely seriously," Ruslan Shaveddinov, a spokesman for the opposition figure, told AFP.
"We are very concerned about his condition and that's why we are demanding immediate access to doctors."
Navalny is still recovering from the poisoning last August, when he began howling in pain and collapsed on a flight from Siberia to Moscow, forcing the plane to make an emergency landing in the city of Omsk.
He was treated for several days by local doctors and eventually flown to Berlin in an induced coma.
Recovering from poisoning
Western experts concluded he was poisoned with the Soviet-era nerve agent Novichok. Russian authorities have repeatedly denied any involvement.
Navalny spent months recovering in Germany, going through physical therapy to re-learn how to walk and even lift a glass of water.
True to usual form, Navalny initially made light of his recent ailments, but on Wednesday turned serious.
"I have the right to ask for a doctor and receive medicine... Jokes aside but this is already bothering me," he said.
The prison service said Navalny is provided with "all the necessary medical assistance in accordance with his current medical condition."
Shaveddinov said Navalny would not have taken the decision to go on hunger strike lightly.
"After a poisoning, no one knows what kind of reaction a body might have in this situation -- and this is very alarming," he said.
Navalny's team declined to provide details as to how the hunger strike will be carried out, but it is an action his allies have experience with.
His ally Lyubov Sobol spent 32 days drinking only liquids in the summer of 2019 after she and other opposition politicians were barred from standing in local elections.
In 2015, Navalny's right-hand man Leonid Volkov and a group of activists in the Siberian city of Novosibirsk went on hunger strike after they were disqualified from local elections.
That action ended after 12 days, when one of the group's members, opposition politician Sergei Boyko, was hospitalised.
Russia's most prominent political hunger striker in recent years was Oleg Sentsov, a Ukrainian filmmaker and outspoken critic of Moscow's annexation of his native Crimea in 2014.
Arrested and jailed in 2015 on terrorism charges, Sentsov went on hunger strike in 2018 demanding that he and Ukrainian political prisoners in Russia be freed.
He ended it after 145 days of subsisting on nutritional supplements -- and glucose drips near the end -- after prison officials announced they would force feed him to ensure his survival.
Sentsov, who was eventually released in a 2019 prisoner swap, lost 20 kilogrammes (44 pounds) during the strike.
Russian law requires the prison service to force feed prisoners if they will not eat voluntarily.
It does not specify how this should be done but rights activists have reported that prisoners are fed a "nutrient mixture" orally, rectally or through a tube.
Navalny "is well aware that a hunger strike is a desperate step," an ally, economist Sergei Guriev, said on Twitter.
"Since he went on a hunger strike, it means that he believes that he has nothing to lose, that the situation is unbearable."