MOSCOW (Reuters) -A lawyer for jailed Kremlin critic Alexei Navalny said on Wednesday that his health was deteriorating and that he was losing a kilogram (2 pounds) a day due to his hunger strike. Navalny, 44, a prominent opponent of Russian President Vladimir Putin, announced a hunger strike last week in protest at what he said was the refusal of prison authorities to treat him properly for acute back and leg pain. He is recovering from what doctors say was a nerve agent poisoning that occurred before he went to prison in February to serve two and a half years. His lawyer, Vadim Kobzev, visited him on Wednesday in the penal colony holding him in Vladimir region east of Moscow and said that Navalny had been diagnosed with herniated spinal discs. “Alexei is walking himself. He feels pain while walking. It is very concerning that the illness is clearly progressing in terms of losing sensation in his legs, palms and wrists,” Kobzev tweeted. In an Instagram post, Navalny said that prison authorities were trying to undermine his hunger strike by roasting chicken near him. Navalny who has been moved to a sick ward in the prison has complained of a high temperature and bad cough. Kobzev said his temperature was oscillating and had been as high as 39 Celsius (102 Fahrenheit) on Monday, though it had fallen to 37C (98.6F) on Wednesday. Navalny has complained of acute back and leg pain and accused authorities of refusing him access to his chosen doctor and of declining to supply him with the right medicine for a condition he has joked darkly could deprive him of the use of both legs. The White House on Wednesday said reports that Navalny’s health is deteriorating were disturbing and urged Russian authorities to ensure his safety and health. Human rights group Amnesty International earlier on Wednesday said Navalny had been incarcerated in conditions that amount to torture and may slowly be killing him. Moscow has cast doubt over his poisoning and paints Navalny as a Western-backed troublemaker bent on destabilising Russia.