Polls opened in a rerun of presidential elections on Tanzania’s semi-autonomous archipelago of Zanzibar that’s being boycotted by the opposition, as security forces increased patrols.

Voting got under way at 7 a.m. in the capital, Zanzibar City, with about 500,000 people registered to cast their ballots. Polls close at 4 p.m. Authorities invalidated the results of the initial Oct. 25 election on the Indian Ocean island nation, citing violations of electoral law.

Tanzanians cast their ballots n Zanzibar
Tanzanians cast their ballots n Zanzibar
Photographer: Tony Karumba/AFP/Getty Images

President Ali Mohamed Shein, who is seeking to extend his five-year rule under the Chama Cha Mapinduzi party, has remained in power pending the new vote. The opposition Civic United Front, which declared its candidate, Seif Sharif Hamad, the winner before official results were confirmed, has said it won’t take part. Hamad’s name is still on ballot papers.

Popular with tourists for its sandy beaches and tropical climate, Zanzibar has seen “contentious and occasionally violent” elections, according to the Washington-based National Democratic Institute. October’s annulment spurred protests dispersed by police. Tanzania’s Daily News reported Friday that authorities on the main island are holding 38 people suspected of criminal acts that include an attempt to blow up the police commissioner’s home.

Observer groups including the European Union said October’s poll was well-organized. Voting on the same day across Tanzania brought to power President John Magufuli, who’s declared war on corruption and government waste in Africa’s third-biggest gold producer.

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