The health of Russian opposition figure Alexei Navalny, who is currently imprisoned in a penal camp, has significantly deteriorated, his chief of staff, Leonid Volkov said.
"Since the end of last week he has been suffering from severe back pain," DPA news agency quoted Volkov as saying in a statement on Wednesday.
Navalny also had symptoms of paralysis in one leg and could no longer walk, he added.
Despite the pain, he had been given only two pills in total, according to Volkov.
"Under all the circumstances known to us, the massive deterioration of his condition can only be cause for extreme concern," chief of staff said.
The Kremlin critic was the "personal prisoner, the personal hostage of (Russian President) Vladimir Putin; a dangerous, crazy murderer", Volkov wrote on Twitter.
"Putin bears the personal responsibility for the life and the health of Alexei Navalny in the torture colony of Pokrow," he added.
The 44-year-old opposition figure was sentenced to imprisonment at the penal camp in Pokrow, about 100 km east of Moscow, in February for violating parole requirements from an earlier sentence, while he was recovering from a poisoning attack in Germany.
Germany, the European Union and the US have repeatedly called for Navalny's release.
Volkov and Navalny's wife, Julia Navalnaya, also complained that the penal camp had not admitted Navalny's lawyers for a scheduled meeting with the opposition politician for the first time, citing other measures within the camp.
Volcov suspected that this was an attempt to cover up a possible admission of Navalny to the prison's hospital.
