Zanzibar's electoral commission has annulled election results in Zanzibar citing "violations of electoral law" and ordered a re-run of the vote.

"I hereby officially announce that this election and all its results have been annulled and there is a need to hold fresh elections," Zanzibar Election Commission Chairman Jecha Salim Jecha said Wednesday in a statement citing "gross violations."

But that decision will be disputed. An official from the opposition Civic United Front branded the move a ploy to rerun a vote it had won.

The main opposition presidential candidate had already declared himself the winner on Monday, ahead of any official announcement of results. Riot police fired tear gas to break up crowds, while foreign embassies warned visitors to avoid political gatherings.

The unfolding election drama comes as Tanzania's ruling party presidential hopeful held the lead with around half the votes counted in the country's tightest ever election, though several veteran politicians are projected to have lost their seats.

Ruling party on track to win

With 133 of 264 constituencies having released results on the third day of counting in east Africa's most populous country, John Magafuli of the long-ruling Chama Cha Mapinduzi (CCM) had won 56.51 percent of votes.

His nearest rival in Sunday's presidential vote, Edward Lowassa of the opposition Chadema party, had 41.67 percent, according to official results announced by the National Election Commission (NEC) late Tuesday.

The unusually tight race could spark tensions with the opposition providing the first credible challenge to the CCM since the introduction of multi-party democracy in 1995.

International observers had largely praised the conduct of Sunday's vote.

"Although there were a few problems in a small number of polling stations, the overall picture was one of millions of people exercising their voting rights in a peaceful environment and demonstrating their commitment to the democratic process," European Union election observer chief Judith Sargentini said.

Outgoing President Jakaya Kikwete, who is not running having served his constitutional two-term limit, ordered the police to boost security to ensure calm in the country of 52 million people, of whom 22 million were registered to vote.

jar/ gb (AFP, Reuters)