Freeman Mbowe, who heads the CHADEMA party, and scores of supporters staged a demonstration Monday in the country’s northern town of Arusha demanding the release of one of its officials and that Kikwete steps down.
The party accuses the president of using security forces to disrupt its activities.
“He has turned himself in to police,” party spokesman Erasto Tumbo told AFP, adding that Mbowe preferred being detained as a sign of protest against the arrests.
“The arrest of our party leaders must stop. We respect the laws, but the police are blocking our activities.”
Police on Monday arrested Wilbrod Slaa, CHADEMA’s secretary general who was beaten by Kikwete in the 2010 presidential election, alongside 26 other party members. They were released on bail late on Tuesday.
Tumbo announced a series of protests to kick off in the capital Dar es Salaam on Thursday to denounce the arrests.
Members of CHADEMA, Tanzania’s main opposition group, have faced court cases since January over demonstrations authorities declared illegal.
During a demonstration in January in Arusha, two opposition members were shot dead when police opened fire to disperse the crowd.