Tanzania briefly detains opposition leader Lissu
Before attending a rally near the Ngorongoro conservation area, Mr Lissu was arrested in the northern town of Karatu.
Chadema, his party, said they were held at a hotel in northern Arusha. Bail was later granted to them.
After President Samia Suluhu Hassan lifted a six-year ban on political rallies imposed by her predecessor, Mr Lissu returned from exile in Belgium in January.
President Hassan’s administration has been criticized for its handling of a controversial port management deal and human rights abuses, according to him.
After being shot at least 16 times, Mr Lissu survived an assassination attempt in 2017. John Magufuli, the late leader, defeated him in the 2020 presidential election.