Ruling party candidate Lenin Moreno looked headed to victory in Ecuador's presidential runoff Sunday but his rival refused to recognize the results, claiming he was the victim of fraud in what could set the stage for protests.

The election in the small Andean nation of 16 million was being watched closely for whether it marked a comeback for leftist candidates after a string of right-wing victories across Latin America,

With almost 96 percent of voting acts counted, the National Electoral Council said Moreno had 51 percent of the vote to banker Guillermo Lasso's 49 percent. A difference of 214,000 votes separated the two candidates with about twice the number of votes still left to count.

Lasso demanded a recount after three exit polls showed him winning. He also questioned why results that took three days to calculate following the first round of voting in February were announced so quickly in Sunday's runoff.

"This is very sickening. We're not going to allow it," said Lasso, who called on supporters to protest the results peacefully but firmly.

"They've crossed a line, which is pretending to abuse the people's will" and install an "illegitimate" government, Lasso said.

So far the only evidence of possible fraud presented by Lasso's campaign are the results in one tiny provincial voting center that it said were reversed when they were reported to electoral authorities in Quito

Thousands of outraged Lasso supporters shouting "fraud" broke through metal barricades and almost reached the entrance of the electoral council's headquarters in Quito before being pushed back by police. A similar scuffle took place outside the electoral offices in Guayaquil.

Moreno supporters celebrated and accused their opponents of trying to disavow results. The head of the electoral council, a favorite punching bag of the opposition, appealed for calm.

"Ecuador deserves that its political actors show ethical responsibility in recognizing the democratic will expressed by the people at the voting booths," said National Electoral President Juan Pablo Pozo. "Not a single vote has been given or taken away from anyone."

Three exit polls, including one that accurately predicted the first-round results, showed Lasso winning by as much as six percentage points. A quick count of voting acts by a respected local watchdog found there was a technical tie with a difference of less than 0.6 percentage points separating the two candidates. The group refrained from saying which candidate had the advantage.

"The moral fraud of the right-wing won't go unpunished," Correa said on Twitter, referring to what Moreno called misleading exit polls that had "lied" to his rival.

Earlier, a jubilant Lasso claimed victory and told supporters in Guayaquil that he would free political prisoners and heal divisions created by 10 years of iron-fisted rule by Correa. Before the election, he said he would evict WikiLeaks founder Julian Assange from the Ecuadorean embassy in London within 30 days of taking office while Moreno has said he will allow him to stay.

With Ecuador's economy slated to shrink by 2.7 percent this year as oil prices remain low and with a majority of citizens stating in surveys that they are eager for change, analysts had been anticipating that Ecuadoreans would back Lasso and join the growing list of Latin American nations shifting to the right.

Yet in the final weeks of the race, Moreno had inched ahead in polls amid an aggressive campaign led by Correa to cast Lasso as a wealthy, out-of-touch politician who profited from the country's 1999 banking crisis.

Authorities deployed thousands of officers to beef up security at vote-processing centers around the country after a contentious first-round election on Feb. 19, in which Moreno fell just short of the required threshold to avoid a runoff.

The vote count dragged on for several days before the official results were announced, provoking accusations of fraud from both sides and angry protests that have injected an unusual degree of volatility in the election results.

Fearing a contested election, church leaders have appealed to both campaigns to accept whatever the results.

Lasso has put forward a pro-business agenda aimed at attracting foreign investment, reducing taxes and generating more jobs and in recent days drew comparisons between continuing a Correa-style government and going down the same path as socialist Venezuela.

Lasso has benefited from ongoing corruption allegations related to bribes Brazilian construction giant Odebrecht paid to officials in Correa's government and a $12 million contracting scandal at state-run PetroEcuador, but analysts say he has not connected with lower-income voters.

While Lasso has said he would evict Assange from the embassy where Ecuador granted him asylum in 2012 to prevent his extradition to Sweden, Moreno has said he could stay, increasing international interest in Sunday's vote.