The authorities in Madagascar have imposed a curfew in Antananarivo ahead of presidential elections on Thursday that are being boycotted by most opposition candidates amid high political tensions.

Angelo Ravelonarivo, the police prefect in the capital, said the measure will come into force at 09:00 pm (1800 GMT) on Wednesday and last until 04:00 am on the next day.

It follows "various acts of sabotage" including the "burning of a polling station", Ravelonarivo told a press conference.

Polls are due to open at 06:00 am and close at 05:00 pm on Thursday for a first round of voting that comes after more than a month of street protests.

Fierce battle

The Indian Ocean island nation has been shaken by a fierce battle between President Andry Rajoelina, who is running for re-election, and most opposition leaders, who have complained about an "institutional coup" in favour of the incumbent.

Ten out of 12 opposition candidates on Tuesday called on voters to shun the elections raising concerns about the vote's regularity.

"We appeal to everyone not to vote. Conditions for a transparent presidential election, accepted by all, have not been met," said Roland Ratsiraka, one of the protesting candidates.

"We do not want to participate in this fraud, it is a joke on Madagascar."

Near daily protest

Since early October, the opposition grouping has led near daily, unauthorised protest marches in the capital that have on average drawn a few hundred supporters and been regularly dispersed by police.

Rajoelina, 49, has brushed off criticism and expressed confidence that he will win another term in the first round.

His government has repeatedly condemned the protests as moved by a "desire to overthrow power" and to "sabotage the electoral process", accusing the opposition of "threatening the stability of the country".