Tanzania said Thursday it was holding the leader of the main opposition party for alleged terror offences, after his arrest in a raid that has triggered international concern.
Chadema chairman Freeman Mbowe and 15 other members were rounded up before dawn Wednesday in a crackdown denounced as a throwback to the oppressive rule of the country's late leader.
"We are holding Freeman Mbowe for plotting terrorism acts including to kill government leaders," Tanzania police spokesman David Misime said in a statement, adding that six other party figures had already been charged in court.
Chadema said police had searched Mbowe's house in Dar es Salaam and seized his laptop and other devices from family members before transferring him to the city's central prison.
Mbowe and the other Chadema officials were arrested in the Lake Victoria port city of Mwanza ahead of a planned public forum to demand constitutional reform.
"The demand for a new constitution has landed me on terrorism charges," Mbowe said in a statement issued by his party.
"I'm ready for these trumped up charges... I believe the world will understand the truth about what we are going through in Tanzania. It will also understand the truth about the fake charges."
The party said police had tried to make Mbowe record a statement on the terrorism allegations but that he refused.
Misime said suggestions he was arrested for organising the meeting were "misleading".
But the region's police commander Ramadhan Ngh'anzi had said earlier that the party members were arrested for organising the meeting that was "banned" because of Covid regulations, adding that Mbowe would be returned later to Mwanza.
The detentions come four months after Tanzania's first female President Samia Suluhu Hassan took office following the sudden death in March of John Magufuli, under whose autocratic rule such clampdowns on the opposition were frequent.
In April, Hassan had reached out to the opposition and vowed to defend democracy and basic freedoms.
There were high hopes Tanzania would be steered away from the heavy-handed and uncompromising leadership of her predecessor.
But the roundup of key Chadema figures was condemned by rights groups and opposition activists as evidence the administration's intolerance of dissent still prevailed.
Amnesty International described the arrests as "arbitrary" and part of an escalating campaign against the political opposition in a country once seen as a beacon of democratic stability in the region.
"Tanzanian authorities must stop targeting the opposition and trying to narrow the space they are able to operate in," said Flavia Mwangovya, Amnesty's deputy director for East Africa.
"These arbitrary arrests and detentions show Tanzanian authorities' flagrant disregard for the rule of law, and human rights, including the rights to freedom of expression and association. These politically motivated arrests must stop."
The United States said Wednesday it was confirming details of Mbowe's arrest but that it would be "very concerning".
Secretary of State Antony Blinken had encouraged Hassan in a July 6 telephone call to protect civil liberties and stressed "the importance of ensuring a democratic, peaceful, free and prosperous future for all Tanzanians," State Department spokesman Ned Price said.
At least 150 opposition leaders, according to the United Nations, were detained after denouncing what they said was massive fraud in an October 2020 election that returned Magufuli and Hassan to power for a second term.