Elections in Zanzibar have been annulled for not being free and fair, the electoral chief on the Tanzanian archipelago has announced.
Rows between rival electoral commissioners had led to physical fights, Jecha Salum Jecha said.
The opposition says the vote on the islands was cancelled because it won.
The main challenger in the national presidential election, Edward Lowassa, said the problems in Zanzibar could be mirrored across the country.
Earlier, he called for the national electoral commission to stop releasing results, alleging the whole process nationwide had been marred by fraud.
The elections in Tanzania are the most competitive in the country’s history, with four opposition parties forming the Ukawa coalition to challenge the ruling CCM’s 54-year grip on power.
Previous elections have turned violent on semi-autonomous Zanzibar, whose two main islands are Unguja, often referred to as Zanzibar, and Pemba.
Mr Lowassa urged his supporters to remain calm and not to engage in street protests.BBC