The leading opposition candidate in the Dominican Republic's presidential election has conceded defeat but defiantly stood by his claim that the country's vote was plagued by irregularities.

Hipolito Mejia, a former president and candidate for the Dominican Revolutionary Party, had failed to recognise the
outcome of Sunday's vote after Danilo Medina of the ruling Dominican Liberation Party claimed victory on Monday. Final results showed he won 51 per cent of the vote compared to 47 per cent for Mejia.

"I assume my role as the leader of the opposition," Mejia told dozens of supporters at a hotel in the capital, Santo
Domingo. However, he called the final vote tally "the result of manipulation and abuse of power."

The election in one of the Caribbean's fastest-growing economies chose the successor to President Leonel Fernandez, who was barred from running again after serving two consecutive four-year terms.

But even as ballots still were being cast on Sunday, the leading parties accused each other of vote-buying. International election observers confirmed some of the reports but said the cases were isolated and had no impact on the final result.

Mejia, in his comments to supporters, also accused the ruling party of using state resources to help boost Medina's
campaign.

Mejia served as president from 2000 to 2004 and left office in the wake of a deep economic crisis set off by a major banking scandal that rocked the country's economy.