Russian opposition activist Alexei Navalny during a court hearing in February.

Russian opposition activist Alexei Navalny during a court hearing in February. / Moscow City Court/Tass via Getty Images

Alexei Navalny, Russia's jailed hunger-striking opposition leader, has been transferred to a prison infirmary after 20 days without food amid a warning from his doctor that he could die "at any minute."

Russian prison authorities said Monday that Navalny has been moved to a medical ward at prison separate from the one where he was being held. He will undergo "vitamin therapy" there, they said.

Navalny's personal physician, Dr. Yaroslav Ashikhmin, said over the weekend that test results he's reviewed show that Navalny is at an elevated risk of cardiac arrest.

"A doctors' commission has decided to move A. Navalny to the regional hospital for convicts," prison authorities announced in a statement, according to The Moscow Times. "Navalny's health condition is assessed as satisfactory and he is examined daily by a general practitioner," it added. "The patient has been prescribed vitamin therapy with his consent."

Navalny allies have said that they are bracing for bad news and that they are planning nationwide protest rallies to call for his release.

On Twitter, Ivan Zhdanov, head of Navalny's Anti-Corruption Foundation, or FBK, said the opposition leader's transfer meant that his condition "has worsened, and worsened in such a way that even the torturer admits it."

Another prominent FBK member, Maria Pevchikh, tweeted it was wrong to say that Navalny "has been transferred to a hospital."

"It's not a hospital, it's just a different penal colony that has the same torturous conditions, same everything, apart from the fact that there are few formally qualified doctors on-site. This changes nothing," she wrote.

Navalny, 44, has been in prison since January when he was arrested after returning from Germany, where he received treatment for a nerve agent poisoning he says Russian President Vladimir Putin ordered.

On March 31, he began a hunger strike to protest what he says is the prison's refusal to treat him for leg and back pain, which he believes could be linked to his poisoning. The Kremlin has said he is exaggerating his condition to gain attention.

In recent days, the harsh Kremlin critic has said that prison officials have threatened to force-feed him.

Navalny is the most prominent opposition figure in Russia, and his death in prison would be an embarrassment to Moscow at a time when it is navigating especially fraught ties with Washington.

Last week, President Biden ordered new sanctions on Russia and expelled several diplomats over the Kremlin's election meddling and alleged role in a major cyberattack that hit U.S.-based computer systems, including some operated by government agencies. Putin's government has denied the accusations.

After the U.S. sanctions were announced, Russia issued a tit-for-tat response, expelling 10 U.S. diplomats.

The Biden administration has warned Moscow of "consequences" should Navalny die in prison, and the European Union said it will hold the Russian government responsible for the opposition leader's health.

Asked about Navalny's condition on Saturday, Biden told reporters: "It's totally, totally unfair and totally inappropriate. On the basis of having the poison and then on a hunger strike."

NPR's Lucian Kim in Moscow contributed to this report.

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Tags: Navalny poisoning  Alexei Navalny