Protest had been planned against alleged disappearances and killings of government critics by security forces

Police in Tanzania have arrested three leaders of the country’s main opposition party in a series of detentions to prevent a planned anti-government protest, the latest in a string of events that analysts and rights groups say erode hopes of a new style of politics under President Samia Suluhu Hassan.

Freeman Mbowe, the chair of the Chadema party, was arrested on Monday in the commercial capital, Dar es Salaam, while speaking with journalists. The party’s deputy chair, Tundu Lissu, was taken from his home in the city in a fleet of 11 vehicles, the party said. Godbless Lema, a central committee member, was also arrested, police said.