Police arrested Tanzania's top opposition figures on Monday, their party said, as the authorities moved to block a mass protest in the commercial capital Dar es Salaam.
Despite an official ban, the opposition Chadema party had vowed to go ahead with the rally over the alleged kidnapping and killing of its members by security forces.
Chadema said its chairman Freeman Mbowe and his deputy Tundu Lissu were both arrested on Monday, while riot police were stationed in key areas across the city to prevent gatherings.
"Demonstration is our constitutional right and we are surprised by the magnitude of force being used by the police to threaten people and suppress our freedom," Mbowe told supporters before being led away by police, according to a video shared by the party online.
Chadema accuses President Samia Suluhu Hassan's government of returning the country to the repressive tactics of her predecessor, John Magufuli.
Hassan took over following Magufuli's sudden death in March 2021 and appeared to signal a more liberal approach, reversing restrictions on opposition rallies and the media.
But Chadema accuses the security forces of being behind the recent disappearance of several members and the killing of Ali Mohamed Kibao, of its national secretariat, who was found dead earlier this month.
Police also blocked a youth day rally by the party in August, arresting dozens of its leaders including Mbowe and Lissu.
Rights groups and Western governments, including the United States, have raised concerns about renewed repression ahead of local elections in November and a general election in late 2025.
Lissu, an opposition stalwart, has been arrested countless times and suffered multiple gunshot wounds in an assassination attempt in 2017.
He returned to Tanzania last year after Hassan lifted the ban on opposition rallies.
Police had alleged that the Chadema protests would be violent.
But in a speech broadcast on X on Sunday, Mbowe said: "I remind Tanzanians that we are going to hold peaceful protests. We are neither carrying any weapons nor planning to violate the peace as some people allege.
"In case some of us will be arrested, hurt or even killed, pray for us and never turn back. We are doing this to make our country a peaceful place to live," he said.
