One of Tanzania's main opposition leaders and former presidential candidate Tundu Lissu was released on bail early on Monday, hours after he was detained by police for allegedly holding an illegal gathering.

Lissu has been holding political rallies across the country since returning from exile in January, where he has criticised President Samia Suluhu Hassan's administration for its human rights record and its handling of a controversial ports management deal.

Lissu, the vice chairman of Tanzania's largest opposition party CHADEMA, was arrested at a hotel along with other party leaders in northern Tanzania's Arusha region on Sunday and released later that evening, Lissu's party wrote on X, the social media platform.

Lissu returned from exile after Hassan lifted a six-year ban on political rallies. He had been in Belgium since he fled in 2020 after losing a presidential election to John Magufuli.

Police said on Sunday that Lissu and three other people were detained for questioning about accusations they were holding an unlawful assembly and preventing police from doing their job.

In a short video posted on X, Lissu was seen along with other party members flashing a V-for-victory hand signal, which is regularly used by CHADEMA.