Angolan police fired tear gas Saturday at hundreds of demonstrators who were protesting in the capital Luanda against the killing of two young opposition activists, an Agence France Presse journalist witnessed. The demonstrators, some wearing T-shirts with the slogan "stop kidnappings and torture", were marching towards the Angolan capital's center when police moved in to disperse the crowd. Opposition party Unita called the rally over the deaths of two activists, who disappeared in May 2012 while organizing an anti-government protest. After months of silence, Angola justice said last week that it had identified four suspects who had allegedly kidnapped and killed the two young men. But information circulating on social networks claimed links to Angolan secret services. Ruling party MPLA has condemned Unita's protest call, saying the opposition was seeking to create "chaos and anarchy". Separately, another opposition party, Casa said that one of its activists was killed early Saturday by presidential security forces after he was detained for putting up posters backing young activists in Luanda. "About 60 militants working with him are still held by police and we are trying to obtain their release," said Casa president Abel Chivukuvuku. Police were not immediately available for comment. In the past two years, young Angolans have become increasingly critical of President Jose Eduardo Dos Santos, who was last year re-elected for a further five years after 33 years at the head of the oil-rich nation.