Russia’s penitentiary service said Monday that it was transferring ailing dissident Alexei Navalny, who is on the 20th day of a hunger strike, to a prison hospital — amid grave fears for his health.

The decision comes a day after the US threatened the Kremlin with "consequences" if President Vladimir Putin’s major domestic opponent dies behind bars, according to Agence France-Presse.

PUTIN CRITIC NAVALNY LOSING FEELING IN HIS HANDS, LEGS AMID HUNGER STRIKE, LAWYER SAYS

Navalny’s private doctors warned during the weekend that he could die at "any minute."

Russian prison authorities, who have barred the 44-year-old’s own medical team from visiting him, said its doctors had decided to move him to a medical facility on the premises of another penal colony in Vladimir, a city about 110 miles east of Moscow.

The state prison service, FSIN, said in a statement Monday that Navalny would be transferred to a hospital for convicts located in another penal colony in Vladimir, a city east of Moscow. (AP Photo/Alexander Zemlianichenko, File)

The state prison service, FSIN, said in a statement Monday that Navalny would be transferred to a hospital for convicts located in another penal colony in Vladimir, a city east of Moscow. (AP Photo/Alexander Zemlianichenko, File)

But they insisted the Kremlin critic’s condition was "satisfactory," adding that he was taking vitamin supplements as part of his medical treatment.

Navalny’s physician, Dr. Yaroslav Ashikhmin, said Saturday that test results he received from Navalny’s family show him with sharply elevated levels of potassium, which can bring on cardiac arrest, and heightened creatinine levels that indicate impaired kidneys.

"Our patient could die at any moment," he wrote on Facebook.

Navalny went on a hunger strike to protest the refusal to let his doctors visit when he began experiencing severe back pain and a loss of feeling in his legs.

Navalny now appears to have a shaven head, although it's uncertain when this photograph was taken. (Instagram)

Navalny now appears to have a shaven head, although it's uncertain when this photograph was taken. (Instagram)

Russia’s state penitentiary service, FSIN, has said that Navalny was receiving all the medical help he needs.

His allies have called for a nationwide rally on Wednesday, the same day that Putin is scheduled to deliver his annual state of the nation address.

Meanwhile, European Union foreign ministers are assessing the bloc’s strategy toward Russia amid the Navalny’s weakening health and in the wake of the military buildup on Ukraine’s borders.

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EU foreign policy chief Josep Borrell already assailed the Kremlin for its arrest and treatment of Navalny on Sunday and insisted he should have access to doctors he trusts.

"All in all, the relations with Russia, are not improving, but the contrary, the tension is increasing in different fronts," Borrell said in a statement.

Navalny was arrested in January upon his return from Germany, where he had spent five months recovering from a nerve agent poisoning he blames on the Kremlin — accusations Russian officials have rejected.

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His arrest triggered widespread protests across Russia.

A court has ordered Navalny to serve 2 1/2 years in the slammer on a 2014 embezzlement conviction he said was fabricated and the European Court of Human Rights deemed to be "arbitrary and manifestly unreasonable."

Last month, the politician was transferred to a notorious penal colony east of Moscow.