One of the lawyers admitted to visit Vasily Aleksanyan, 36, on Saturday and Monday said that his client had told him that he was normally kept chained to the bed, and was only released when he had visitors.
Aleksanyan had earlier written a complaint to "find out who gave the order [for the chains] and why," said Gevorg Dangyan. The lawyer also said that, apart from this, admittedly major drawback, conditions in the ward seemed satisfactory.
The decision to move Aleksanyan, 36, who has been accused of embezzling about $330 million from former Yukos production unit Tomskneft and shares worth $493 million from other oil companies, as well as of laundering stolen assets, was made following demands from lawyers and former colleagues.
The prosecution earlier insisted he should undergo medical treatment in jail. However, a Moscow court suspended Aleksanyan's trial due to his worsening health.
Jailed ex-Yukos CEO Khodorkovsky, the founder of what was once Russia's largest oil producer, declared a hunger strike on January 30 demanding medical treatment for Aleksanyan. He called off his protest some two weeks later when Aleksanyan was admitted to hospital.
Aleksanyan earlier claimed that that the reluctance of the Russian authorities to provide him with medical treatment was due to his refusal to assist prosecutors with new charges against Khodorkovsky.
The latest charges against Khodorkovsky and his one-time business partner Platon Lebedev, both convicted in 2005, include stealing government shares, illegal oil trading, and laundering $25 billion earned from oil sales in 1998-2004.
Khodorkovsky has consistently maintained his innocence of all charges against him, saying that his imprisonment is a direct result of his support for Russia's tiny pro-Western opposition.
Yukos collapsed after claims of tax evasion in 2004 which led to the company being broken up and sold off to meet creditor claims. The bulk of its assets were bought through liquidation auctions by government-controlled oil company Rosneft. Yukos was officially dissolved in 2007.