Mauritania's opposition candidates said yesterday's presidential election had already been marred by fraud and voter intimidation just hours after polling began in the northwest African desert state.

"First indications point to massive fraud across the country," one of the six candidates, Ahmed Ould Daddah, told reporters after casting his vote in a school in the capital Nouakchott.

He added that "stuffing of ballot boxes began at 7:00 am," when polls opened.

Another candidate, Mohamed Khouna Ould Haidallah, who was briefly detained by police on Thursday along with six of his entourage and accused of plotting a coup, said there had been "all sorts of intimidation" of voters.

The New York-based group Human Rights Watch has expressed fears the election will not be free and fair.

But the incumbent president, Maaouiya Ould Taya, said after casting his vote yesterdat that voting was "totally transparent".

The election would "no doubt be considered an example for those who are interested in the establishment of democracy in the world," he added after he voted in Nouakchott.

The arrest of Ould Haidallah prompted the International Federation of Human Rights Leagues to call for the poll to be suspended under a law, which says it must be put off if a candidate is prevented from standing by illness, death or arrest.

Although Mauritania is one of the world's least developed nations, voters are using a high-tech identity card when they cast their ballots to prevent fraud.

International observers have not been invited to witness the vote. – Sapa-AFP.