Reporters Without Borders is very worried about opposition leader and former prime minister Mir Hossein Mousavi, the owner of the suspended newspaper Kalameh Sabaz, who was hospitalized two days ago in Tehran after suffering a heart attack. Mousavi has been under house arrest in an unknown location for more than 18 months. "The conditions of Mousavi's house arrest have damaged his health and he must be released at once," Reporters Without Borders said. "We urge the Supreme Leader, Ayatollah Khamenei, to act quickly to avoid exposing him to further danger. We will hold Khamenei responsible for anything that happens to Mousavi or to the many other journalists who are being kept in detention despite their poor health." Mousavi, 72, was hospitalized under close surveillance by many intelligence ministry agents and Revolutionary Guards after suffering the heart attack on 22 August. The lack of information about his state of health is disturbing. His family is being pressured by the authorities and is unable to say anything. Mousavi and his wife, the best-selling writer Zahra Rahnavard, were arrested and placed under house arrest on 24 February 2011. Former parliamentary speaker Mehdi Karoubi, the owner of the suspended newspaper Etemad Melli, was also placed under house arrest the same day. They have been denied all of their rights ever since. Karoubi also has many health problems. His wife, Fatemeh Karoubi, the editor of the magazine Iran Dokhte, was also arrested but was released in September 2011. "Holding political prisoners incommunicado is tantamount to enforced disappearance and violates international law," Reporters Without Borders said. "The Iranian authorities nonetheless resort to such methods systematically with journalists and netizens."