Santo Domingo - The presidential election Friday in the Dominican Republic started in calm, as over 5.7 million voters prepared to choose their leader with centre-right incumbent Leonel Fernandez as the favourite among seven candidates.

Polling stations opened at 6 am (1200 GMT) and were set to close 12 hours later.

Dominican electoral authorities called upon Dominicans to exercise their right to vote and noted that the country remained calm despite an incident linked to the election hours earlier.

On Thursday, supporters of Fernandez's Party for Dominican Liberation (PLD) and of the social democratic Dominican Revolutionary Party (PRD) of his main rival Miguel Vargas clashed, and four PLD supporters were injured. Still, the current campaign has been described as one of the least violent in the Caribbean country's history.

Vargas voted early in Santo Domingo, while incumbent hopeful President Fernandez was planning to cast his ballot in the afternoon.

"Beautified opinion polls say Fernandez will win, but the true polls say we will win. We are now at the most important opinion poll, on May 16 (election day) and we will win this one," Vargas told reporters after casting his ballot.

Most opinion polls have said that Fernandez is likely to get at least 55 per cent of the votes, granting him re-election without need for a runoff. Vargas is expected to get around 37 per cent of the vote, according to opinion polls. (dpa)