Jailed Kremlin critic Alexei Navalny said he could be locked up in solitary confinement after being accused of numerous minor infractions, and posted the first picture on Monday of himself from prison, a grainy image showing his head had been shaven.
The fate of Navalny, one of President Vladimir Putin's most prominent critics, is in focus after he said on Thursday that being woken up by a guard every hour during the night amounted to torture and that his appeal for treatment for acute back and leg pain had been ignored.
More than 20 medical professionals on Sunday published an open letter demanding the 44-year-old opposition politician get proper care.
"We fear for the worst. Leaving a patient in this condition ... may lead to severe consequences, including an irreversible, full or partial loss of lower limb functions," the letter said.
Prison authorities, after examining Navalny last week, declared his condition to be stable and satisfactory. The Kremlin on Monday declined to comment on the medics' letter.