Freeman Mbowe was arrested last week while preparing for a meeting on new constitution proposals.
Tanzanian riot police have detained a number of protesting supporters of arrested opposition leader Freeman Mbowe, his party has said, as a “terrorism” case against him was postponed.
Mbowe and other officials from the main opposition party, Chadema, were arrested last month ahead of a planned conference to demand constitutional reforms.
The 59-year-old has been charged with terrorism financing and conspiracy and is being held in a prison in the financial capital Dar es Salaam, in a case that has triggered concern among rights groups and some Western nations.
Mbowe was due to appear in court on Thursday via a video link but the case was postponed to Friday because of connection problems, his defence lawyer Peter Kibatala said. Mbowe is now expected to be brought to court on Friday.
Chadema supporters waving placards saying “Mbowe is not a terrorist” and “Free Freeman Mbowe” gathered outside the court.
Police responded by arresting protesters, the party said on Twitter. It was not immediately clear how many were detained.
State prosecutors say the terrorism charges against Mbowe did not relate to his planned activities in Mwanza, where he had been preparing for a meeting to discuss the constitution, but to alleged offences that occurred last year in a different part of Tanzania.
Mbowe’s arrest came four months after President Samia Suluhu Hassan, Tanzania’s first female leader, took office following the sudden death of her predecessor, John Magufuli.
There had been hopes that Hassan would usher in change from the dictatorial rule of her predecessor, nicknamed the “Bulldozer” for his uncompromising style.
On Wednesday, a top United States official expressed concern about Mbowe’s arrest.
“We have expressed our concern about the treatment and imprisonment of the opposition leader Mbowe,” Victoria Nuland, Under Secretary of State for Political Affairs, told reporters.
Nuland, on a tour of several African countries, was speaking at the end of a visit to Tanzania during which she met President Hassan, Tanzania’s foreign minister as well as opposition leaders.