MOSCOW — "Allow a doctor to see my dad."

The plea, tweeted Saturday by Alexei Navalny’s daughter, came amid a global wave of dismay over Russian authorities’ refusal to let President Vladimir Putin’s leading critic see his physician as his condition has reportedly worsened.

Navalny is on his 20th day of a hunger strike in a Russian prison. Daria Navalnaya, his 20-year-old daughter, is in California studying at Stanford University.

Navalny’s press secretary Kira Yarmysh has tweeted that Navalny is “dying,” and several doctors said he could go into cardiac arrest at any time. Yarmysh said he had days to live.

Navalny’s team on Sunday announced new protests in cities across Russia for Wednesday evening.

“Have you ever seen with your own eyes how they kill a person?” his representatives asked in a statement. “You are seeing it right now. . . . They are killing Alexei Navalny. In a terrible way. In front of us all.”

Dozens of writers, historians, actors and celebrities signed a letter published in the Economist and Le Monde on Friday, calling on Putin to allow Navalny to see his doctor. President Biden on Saturday called Russia’s actions “totally unfair” and “totally inappropriate.”

Anastasiya Vasilyeva, Alexei Navalny’s physician, said she and other doctors waited for two hours but were not allowed to see the opposition leader. (Anastasiya Vasilyeva's Team via AP)

U.S. national security adviser Jake Sullivan told CNN on Sunday that the Biden administration has warned Russia that there will be consequences if Navalny dies in prison. He did not elaborate.

Navalny’s wife was allowed to visit him in prison for the first time last week. Yulia Navalnaya said she spoke to her husband by telephone through glass. She said he had difficulty speaking and had to put the receiver down and lie down because he was so weak.

Navalny’s Twitter account said Friday that authorities had threatened to put him in a straitjacket and force-feed him. He has no access to the account, but lawyers have regular contact with him, and posts are made by his team.

The post said: “Now I just point a finger at the point of the law and say: Sorry. Don’t force-feed me.”

Navalny was poisoned with a chemical weapon in the same class as the Soviet-era nerve agent Novichok while traveling from Siberia last August. U.S. and European authorities have blamed the attack on Russian state agents; they’ve responded with sanctions against Russian organizations and individuals.

For two days after the attack, Russian authorities refused his family’s demands to allow his evacuation to Germany for medical treatment. The Kremlin says there is no evidence Navalny was poisoned, and prosecutors have declined to open a case into the incident.

Navalny suggested Friday that his recent symptoms, which include numbness in his legs and one hand, could be related to that poisoning, or a new state attack.

“They are afraid that it will turn out that the loss of sensation in my limbs may be associated with poisoning. The old one. Or something new, I wouldn’t be surprised.”

His Twitter feed has recounted efforts by Russian prison authorities to break him during his hunger strike, including slipping candies into the pockets of his prison clothing and frying chicken in front of him while recording his reaction.

The doctors who warned that Navalny’s life was in danger included Yaroslav Ashikhmin, Alexei Erlikh, Alexei Kashcheyev, Alexander Polupan and Andrei Volna.

“We, the doctors, are ready to act,” tweeted several physicians associated with Anastasia Vasilyeva, a Navalny ally who heads a small independent medical workers’ union. “The question remaining is whether the penal colony is willing to cooperate to save the life of Navalny.”

The group said high potassium levels in Navalny’s blood were indicative of kidney failure and that severe heart-rhythm disturbances threatened cardiac arrest.

“Action must be taken immediately,” the group said. Others posted about the urgency of the situation on social media.

“We are talking about life and death, with no exaggeration,” tweeted Navalny aide Ivan Zhdanov, who fled Russia but whose father was recently arrested over protests in the country.

“Navalny could die at any moment,” tweeted Maria Pevchikh, an investigator with Navalny’s Anti-Corruption Foundation. “This moment may be today. We require urgent, immediate admission from doctors.”

Navalny was arrested when he returned from Germany in January and imprisoned for failing to report to authorities as part of his probation conditions in an earlier case. He has said he couldn’t report because he was being treated in Germany. He says the many charges against him are political cases intended to silence him and deter others.

Jailed Kremlin critic Alexei Navalny was in court on Feb. 5, accused of slandering a World War II veteran who appeared in a promotional video for Putin in 2020. (Reuters)

Navalny’s Friday post said he had a right to see a doctor and a right to refuse to be force-fed.

“I protest not only for myself, but also for hundreds of thousands of those who have no rights,” it said.

Russian state media have claimed Navalny is a Nazi and a CIA agent, asserting that he is motivated only by money. Authorities claim his searing anti-corruption exposés are fabricated.

State media recently dispatched Maria Butina to his prison, where she loudly berated him and told him his jail conditions were better than a hotel. Butina was imprisoned in the United States as an unregistered Russian agent.

Russia’s prosecutor general on Friday commenced action to designate Navalny’s Anti-Corruption Foundation and his political network of regional offices known as Navalny Headquarters as an extremist organization.