Amnesty International is urging China to free an ethnic Uighur activist whose family says he is being tortured in prison and is in failing health. The group renewed its call yesterday for the release of Ablikim Abdureyim, the son of prominent exiled Uighur leader Rebiya Kadeer. Abdureyim was convicted in 2007 of involvement in secessionist activities and sentenced to nine years in prison. He told relatives who visited him in prison in Urumqi last week that he was placed in solitary confinement more than a month ago, and that his health has deteriorated. Amnesty International says the harsh treatment began after Abdureyim witnessed an incident that prison officials wanted to cover up. He told family members that he refused to sign a document denying he witnessed the unspecified ‘controversial incident.’ Beijing says Kadeer instigating deadly 2009 ethnic riots in Urumqi, the capital of China's mostly Muslim Xinjiang region. The U.S.-based activist denies the accusation and says Chinese authorities are persecuting her family members in China.