The daughter of Kremlin critic Alexei Navalny called on Russian authorities on Sunday to allow a doctor to treat her father in prison, a day after a group of medical professionals warned he is at risk of kidney failure.

Navalny, a vocal opponent of Russian President Vladimir Putin, began a hunger strike on March 31 in protest of what he said was the refusal of prison authorities to offer him proper medical care for acute back and leg pain.

"Allow a doctor to see my dad," tweeted Navalny's daughter, Dasha.

European officials 'extremely concerned'

Germany's foreign minister also called on Moscow to give Navalny adequate medical care.

"We urgently demand that Alexei Navalny receive adequate medical treatment and access to doctors he trusts. His right to medical care must be granted without delay," Foreign Minister Heiko Maas told Bild newspaper.

Meanwhile, Maas' French counterpart, Jean-Yves Le Drian said his country is "extremely concerned" over Navalny's health. 

"Navalny's situation is extremely concerning," Le Drian told France 3 television on Sunday.

"I hope that measures are taken to ensure Navalny's physical integrity, but also his freedom," he said. "There is a major responsibility here for President Putin."

"There is truly an authoritarian drift in Russia," Le Drian added. "Russia is responsible for Navalny's health, it must assume its role."

The comments came as EU foreign ministers set a date to discuss Navalny's health at a meeting on Monday. "At tomorrow's Foreign Affairs Council in Brussels, EU foreign ministers will also address Navalny's situation," said Maas.

US threatens 'consequences'

US President Joe Biden's national security adviser Jake Sullivan also denounced Navalny's treatment, saying that the US government has told Russia that "there will be consequences" if he dies in prison. Sullivan made the comments on CNN's "State of the Union" on Sunday. 

"We have communicated to the Russian government that what happens to Mr. Navalny in their custody is their responsibility and they will be held accountable by the international community," Sullivan said.

"In terms of the specific measures that we would undertake, we are looking at a variety of different costs that we would impose and I am not going to telegraph that publicly at this point, but we have communicated that there will be consequences if Mr. Navalny dies," he added.

Prison authorities say they have offered Navalny proper medical care, but that he has refused the treatment in favor of being treated by a doctor of his choice from outside the facility, a request that authorities have declined.

A medical trade union with ties to the 44-year-old dissident said on Saturday that he was in critical condition, citing medical tests that it said showed that Navalny's kidneys could soon fail, leading to cardiac arrest.

Celebrities call for treatment

The same day, a group of celebrities penned an open letter calling on Putin to allow Navalny to receive medical treatment from a doctor of his choice. The group included actors, writers, and celebrities such as J.K. Rowling, Benedict Cumberbatch and Jude Law.

The open letter was published in Le Monde newspaper in France, The Economist, La Repubblica in Italy and Der Spiegel in Germany.

"Alexei Navalny is exhibiting symptoms of a severe neurological disorder — constant back pain and the loss of sensation in his legs and hands. In addition, he is suffering from a severe cough and fever. As a Russian citizen, he has the lawful right to be examined and treated by a doctor of his choice," the letter said.

A group of opposition regional lawmakers also called on Putin on Saturday to make sure that Navalny received proper treatment. Navalny has said that prison authorities are threatening to put him in a straightjacket to force-feed him unless he abandons his hunger strike.

In an interview with the BBC, however, Russia's ambassador to Britain accused him of attention-seeking.

"He will not be allowed to die in prison, but I can say that Mr. Navalny, he behaves like a hooligan, absolutely," Ambassador Andrei Kelin said in the interview. "His purpose for all of that is to attract attention."

Navalny allies call for protests

On Sunday, allies of Navalny also said they planned to stage large-scale street protests on April 21 to draw attention to his deteriorating health.

"There are circumstances under which you have to act quickly, otherwise there will be irreparable damage," the call for protest read.

Around 457,000 people have already signed up for the protest on Navalny's website.

Navalny was jailed for two and a half years in February for parole violations that he said were fabricated. He was arrested in January upon his return to Russia from Germany, where had been treated after being poisoned with the nerve agent Novichok.

lc/nm (dpa, Reuters, AFP)