The International Federation for Human Rights (FIDH) and its member organization the Vietnam Committee on Human Rights (VCHR) have addressed today an open letter to the Prime Minister of the Socialist Republic of Vietnam requesting the immediate release of Thich Huyen Quang, the Supreme Patriarch and the second-ranking Thich Quang Do, of the Unified Buddhist Church of Vietnam (UBCV), who are under detention for the last 26 years for their peaceful advocacy of religious freedom, democracy and human rights. The organizations also expressed deep concern on the case of Buddhist monk Thich Tri Khai, who disappeared on 7th May after being submitted to intensive Police interrogations. FIDH and VCHR have called upon the prime minister to address the issues of ill-treatment of UBCV monks, and nuns by security police and to uphold the international human rights standards on freedom of religion and belief, as guaranteed by the Universal Declaration of Human Rights.