Syrian authorities have detained an activist who headed a recently formed group promoting peaceful and democratic change in Syria, a human rights group said Sunday. The Damascus-based Syrian Organization for Human Rights said Fidaa al-Hourani went to the state security's intelligence headquarters Sunday morning in the northern town of Hama after being summoned and has not been seen or heard of since then. "This phenomena of political detentions must stop," SOHR said in a statement made available to The Associated Press. Individuals summoned to state security who do not immediately reappear are generally assumed in Syria to be under arrest. Al-Hourani, 51, a writer, was elected on Dec. 1 president of the newly formed National Council of the Damascus Declaration - a group of pro-democracy activists working for democratic change in Syria.