Tanzania police stormed an opposition party meeting at a Dar es Salaam hotel on Monday afternoon and ordered them to stop it, saying it was illegal.
The Chama cha Demokrasia (Chadema) chairman Freeman Mbowe, former presidential flag bearer Edward Lowassa and other party leaders were then escorted to the Central Police Station, where they were interrogated.
The police arrived at the city hotel at 2pm (1100 GMT) where the Chadema’s central committee members were meeting. According to Halima Mdee, Chadema women’s wing (Bawacha) chairperson, the meeting was to discuss whether the party would go ahead with plans to hold countrywide demonstrations starting September 1.
Chadema lawyer Tundu Lissu said those grilled by the police included Mr Mbowe, Mr Lowassa, the secretary-general Dr Vincent Mashinji, vice chairman (Isles) Said Issa Mohamed and the deputy secretary general (Mainland) John Mnyika.
In the wake of the killing of four policemen by gunmen outside a Dar es Salaam bank last week, police banned internal meetings of political parties saying they are being used to plot violence.
The Chadema leaders were released on police bail at around 7.20pm (1620 GMT). After their release, Mr Mbowe said they were interrogated for contempt of police order which banned political meetings.