An officer walks outside the IK-3 penal colony, which houses a hospital where jailed Kremlin critic Alexei Navalny was…
An officer walks outside the IK-3 penal colony, which houses a hospital where jailed Kremlin critic Alexey Navalny was reportedly transferred, in Vladimir, Russia, April 20, 2021.

Doctors associated with jailed Kremlin critic Alexey Navalny say they have been barred from seeing him, despite reports he is seriously ill from an ongoing hunger strike. 

According to his personal physician, Dr. Anastasia Vasilyeva, she and three other medical experts tried to visit Navalny at a prison clinic and were denied entry. They said they waited outside prison gates for hours. 

"It's a show of disrespect and mockery of the doctors," Vasilyeva said in a tweet, noting Navalny's "life and health are clearly in danger." 

FILE - Russian opposition politician Alexey Navalny attends a court hearing in Moscow, Russia, Feb. 20, 2021.

On Sunday, Navalny was moved from a penal colony east of Moscow to the hospital at a prison in Vladimir, which is 180 kilometers east of Moscow. 

On Monday, Russia's prison service said Navalny's condition was "satisfactory," but another one of his physicians, Dr. Yaroslav Ashikhmin, said Navalny was suffering from high levels of potassium, which could cause a heart attack, and increased creatinine levels, showing potentially weakened kidney function. 

Navalny, 44, began his hunger strike at the end of March to protest what he said was a lack of medical care for severe back and leg pain. 

Navalny survived a near-fatal poisoning last year and was arrested when he returned to Moscow in January following lifesaving treatment in Germany. The Kremlin denies any role in the poisoning. 

He was sentenced to two-and-a-half years in prison in February on an embezzlement charge and was being held at the Pokrov correctional colony, which he described as "a real concentration camp."   

The United States and other countries have sanctioned Kremlin officials over the poisoning, and many are calling for Navalny's release.   

As Navalny's health deteriorates, Russian authorities have asked the Moscow prosecutor's office to declare Navalny's organization, the Foundation for Fighting Corruption, an extremist organization. 

Navalny allies have called for nationwide protests Wednesday, when Russian President Vladimir Putin is scheduled to deliver his annual state of the union speech.