A day after Julian Assange’s lawyers said he was too ill to appear via video link for a court hearing, the United Nations has expressed serious concerns that the WikiLeaks founder is suffering “psychological torture.” Nils Melzer, the U.N. special rapporteur on torture, visited Assange in a high-security London prison this month. “Mr. Assange has been deliberately exposed, for a period of several years, to progressively severe forms of cruel, inhuman or degrading treatment or punishment, the cumulative effects of which can only be described as psychological torture,” Melzer said in a statement, Reuters reports. Melzer added that, if extradited to the U.S., Assange would be “exposed to a real risk of serious violations of his human rights, including his freedom of expression, his right to a fair trial, and the prohibition of torture.” The U.S. is seeking the extradition of Assange for one of the biggest ever leaks of classified information.