The defeated candidate in the Dominican Republic's presidential election has challenged the official result but vowed to fight for reform as head of the opposition, appearing to concede the vote. Ruling party candidate Danilo Medina on Tuesday was declared the winner of the weekend election, defeating former president Hipolito Mejia, who alleged "manipulation and abuse of power". "The results offered to the country by the Central Electoral Board are the product of manipulation and abuse of power and are not an expression of the free will of the people, which is unacceptable," he said in a televised speech. But Mejia appeared to accept the loss, saying: "I will assume my role as leader of the opposition in defense of the national interest and the preservation of the peace and tranquility of the Dominican family." With all election precincts reporting, Medina, 60, garnered 51.21 percent of Sunday's vote, against 46.95 percent for Mejia, election authorities said. Medina, who will take the oath of office on August 16, represents the Dominican Liberation Party (PLD) of outgoing President Leonel Fernandez, who has served three terms in office. His running mate in the race was Fernandez's wife Margarita Cedeno. Claiming victory on Monday, Medina offered his "thanks to the Dominican people" and vowed to be a leader for all the people. The last time Medina faced off against Mejia in a presidential election, back in 2000, he was defeated. But this time voters were apparently swayed by his promises to raise their standard of living, improve the plight of farmers and work for free trade deal with neighboring Haiti, among other campaign themes. Mejia, 71, was president from 2000 to 2004 in the country of 10 million inhabitants, which shares the mountainous island of Hispaniola with Haiti. An Organization of American States monitoring team praised the vote, issuing a statement Monday saying it showed the Dominican Republic's "maturity" as a democracy. Mejia meanwhile vowed to fight for electoral reform, accusing Fernandez of "blatant interference" and slamming the "bias" of the head of the election board, calling it a "throwback to the era of totalitarian governments."