Alexei Navalny
Alexei Navalny Reuters

Jailed Kremlin critic Alexei Navalny risks cardiac arrest "any minute" as his health has rapidly deteriorated, doctors warned on Saturday, according to AFP.

Navalny, one of Russian President Vladimir Putin's most prominent critics, was arrested on January 17 for alleged parole violations after returning from Germany, where he had been recovering from being poisoned with a military-grade nerve agent.

He was later sentenced by a Russian court to a three-and-a-half-year sentence, though his lawyer said he would serve only two years and eight months in jail because of time he has already spent under house arrest.

In late March, Navalny launched a hunger strike to protest the authorities’ failure to provide proper treatment for his back and leg pains.

Earlier this month, he was moved to a medical facility to be treated for a possible respiratory illness.

Navalny's personal doctor Anastasia Vasilyeva and three more doctors including cardiologist Yaroslav Ashikhmin have asked prison officials to grant them immediate access.

"Our patient can die any minute," Ashikhmin said on Facebook on Saturday, pointing to the opposition politician's high potassium levels and saying Navalny should be moved to intensive care.

"Fatal arrhythmia can develop any minute."

Having blood potassium levels higher than 6.0 mmol (millimole) per liter usually requires immediate treatment. Navalny's were at 7.1, the doctors said.

"This means both impaired renal function and that serious heart rhythm problems can happen any minute," said a statement on Vasilyeva's Twitter account quoted by AFP.

Navalny's spokeswoman Kira Yarmysh, who accompanied him when he collapsed on a plane after the poisoning in August, said the situation was critical again.

"Alexei is dying," she said on Facebook. "With his condition it's a matter of days."

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