An international rights group called on the Syrian government Saturday to reveal the fate of a prominent lawyer and rights activist who disappeared this week. New York-based Human Rights Watch said three Syrian rights group have told the organization that Haitham al-Maleh, 78, is believed to have been detained by one of Syria's intelligence agencies known as Political Security. Al-Maleh was summoned by security agents for unknown reasons on Wednesday and has not been seen since, eight Syrian rights groups said in a joint statement Thursday sent to The Associated Press. Two groups told Human Rights Watch they believe the reason behind al-Maleh's arrest is a telephone interview he gave on Oct. 12 to an opposition television station in which he criticized the Syrian authorities for their restrictions on freedom of expression, the international rights group said. "Given Syria's usual response to criticism, it would come as no surprise if they have disappeared this 78-year-old human rights activist for no other reason than a television interview," said Sarah Leah Whitson, Middle East and North Africa director at Human Rights Watch. "If the government is holding him, they should say so and release him." Al-Maleh was imprisoned from 1980 until 1986 after he demanded constitutional reforms. He was sentenced by a military court in 2006 to 10 days in prison for insulting a government employee. Since coming to power in 2000, President Bashar Assad has freed political prisoners and passed laws aimed at liberalizing the state-controlled economy. But he has also clamped down on political activists.