Tanzanians will go to the polls on November 27 in the first real political test of President Samia Suluhu Hassan's administration.

The official date was announced this week as security agencies and the main opposition party, Chadema, clashed over the right to assemble, which the authorities saw as a plot to sow chaos in the country.

Hopes for a smooth conduct of the civic poll, which will lay the groundwork for next year's general elections, were dealt a severe blow after a heavy-handed police response to Chadema's plan to hold a rally in Mbeya, south-west Tanzania.

The party's leaders and some supporters, more than 500 of them, were arrested ahead of the rally on Monday before being released and sent back to their homes.

The incident overshadowed the long-delayed announcement of the election date by the Ministry of Local Government and Regional Administration (Tamisemi), which was made with fanfare in the capital Dodoma on Thursday.

Police violently enforced a ban on the opposition rally, which was to mark the annual International Youth Day.