Alexey Navalny, a critic of Russian President Vladimir Putin who has been jailed for several months, is reportedly suffering the effects of his hunger strike, according to his wife, who visited him Tuesday.
Navalny, 44, began his hunger strike at the end of March in protest over what he said was a lack of medical care for severe back and leg pain. His wife said he is having a hard time speaking.
"He is still as cheerful and upbeat as ever," Yulia Navalnaya wrote in an Instagram post. "He speaks with difficulty, though, and from time to time he hangs up the phone and leans on the table to take a break. He has lost a lot of weight ... and weighs 76 kg at 190 (cm)."
Navalny has reportedly lost 16 kilograms (35 pounds) since his imprisonment in February.
According to The Associated Press, Navalny's team said authorities are threatening to force-feed him.
Navalnaya said prison officials will still not let a doctor examine her husband.
"I've never seen skin so tight around one's skull, but I know he's not going to give up," she wrote.
Prison staff said they offered Navalny medical treatment, but he refused it. Navalny had been moved to the prison clinic earlier this month with a bad cough and fever.
On Tuesday, the Russian prisons service said a panel of doctors assessed Navalny's health as satisfactory. They said he had been transferred out of the clinic and back to the main part of the prison on April 9, according to Reuters, which cited the RIA news agency.
Also Tuesday, Navalny threatened to sue the prison for refusing to give him a copy of the Quran, AP reported. Navalny reportedly said studying the Islamic holy book was a goal of his while in prison.
Navalny survived a near-fatal poisoning last year and was arrested when he returned to Moscow in January following lifesaving treatment in Germany.
He was sentenced to 2 ½ years in prison in February on an embezzlement charge and is 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.