Costa Rica's National Liberation Party presidential candidate Laura Chinchilla waves to supporters after voting at a polling station in Sunday's election. (Esteban Felix/Associated Press)

Costa Ricans have elected their first woman president as the ruling party candidate won in a landslide after campaigning to continue free market policies in Central America's most stable nation.

With most of the votes from Sunday's election counted, Laura Chinchilla held a 22-point lead over her closest rival. Her 47 per cent share of the vote was well beyond the 40 per cent needed to avoid a run-off.

The 50-year-old protege of the current president, Nobel Peace Prize laureate Oscar Arias, promised to pursue the same economic policies that recently brought the country into a trade pact with the U.S. and opened commerce with China.

"Today we are making history," said Chinchilla, who will be the fifth Latin American woman to be elected president when she takes office in May. "The Costa Rican people have given me their confidence, and I will not betray it."

The closest contender, Otton Solis of the Citizens Action Party, got 25 per cent of the votes. He and the other main rival, Libertarian Otto Guevara, quickly conceded defeat.

It was unclear, however, whether Chinchilla's National Liberation Party would gain a majority in congress.

Analyst Heather Berkman of the Eurasia Group said coalition building without a majority would likely delay or derail controversial fiscal reforms to shore up government finances and energy deregulation.

Libertarian party wins 21 per cent of vote

The third-place candidate, Guevara, congratulated Chinchilla as "our president," but he also pointed out the new political muscle of his tax-bashing Libertarian Movement Party. He won 21 per cent of the vote.

Arias' economic policies helped insulate Costa Rica from the world economic crisis as he kept a high profile on the world stage as a negotiator in Honduras' political crisis after a coup deposed President Manuel Zelaya in June.

Critics of the Arias government, in which Chinchilla served as vice-president, contended its policies catered to big developers to boost the economy at the cost of the nation's fragile ecosystems.

But most Costa Ricans were reluctant to shake up the status quo in a country with relatively high salaries, the longest life expectancy in Latin America, a thriving ecotourism industry and near-universal literacy.

Chinchilla, the mother of a teenage son, is a social conservative who opposes abortion and gay marriage. She appealed both to Costa Ricans seeking a fresh face and those reluctant to risk the unknown.

As a female president, she would follow an increasingly common trend in many Latin American countries: Nicaragua, Panama, Chile and Argentina have all elected women as presidents.

Alfredo Fernandez, 77, said he has always voted for the National Liberation Party, but this time his ballot was special.

"It is an honour to be able to have a woman president," he said.

Even Costa Ricans on the margins of society backed Chinchilla.

Heizel Arias, a 24-year-old single mother, voted at a prison where she is serving an eight-year sentence for drug smuggling.

"I voted for Laura Chinchilla because she has promised to fight for women," Arias said. "She was the only one who visited us and told us her plans, and I believe in her."