Russian authorities on Thursday said jailed opposition leader Alexei Navalny was in good  health, after reports by his staff that his condition was deteriorating in a prison camp.

The prisons authority said the 44-year-old was examined on Wednesday, according to a report by news agency Interfax.

“Alexei Navalny was among those who underwent an examination, which showed that he is in generally good and stable health,’’ it said.

Navalny’s chief of staff Leonid Volkov said he would interpret this to mean that Navalny was in hospital. “Something very bad is happening,’’ Volkov wrote on Twitter.

Volkov added that Navalny’s lawyers were currently not being allowed in to see him “without explanation of the reasons.’’

Earlier, Navalny’s lawyers had said he was suffering from back pain and paralysis in one leg.

Volkov has called the IK-2 camp where Navalny is being held in Pokrov, 100 kilometres east of Moscow, a torture camp and said the opposition leader was being held as personal hostage of President Vladimir Putin.

Navalny was sentenced to imprisonment at the penal camp in early February for violating parole requirements from an earlier sentence, while he was recovering from a poisoning attack in Germany.

Navalny has blamed poisoning on Putin and said his imprisonment was a personal act of vengeance for surviving the attack.

Germany, the European Union and the United States have repeatedly called for Navalny’s release.