President of Bolivia Evo Morales speaks during a press conference on October 24, 2019 in La Paz, Bolivia. Getty

La Paz, Bolivia — President Evo Morales on Thursday declared himself victor of the weekend election, stirring more anger among his opponents who have protested for days claiming fraud in the vote count, while the U.S., Brazil, Argentina and Colombia joined in calling for Bolivia to hold a runoff between the incumbent and his top challenger.

Electoral authorities, meanwhile, announced late in the day that voting would have to be held again in five spots in the Amazonian Beni region because of irregularities in Sunday's vote. They said the re-votes to be held November 3 wouldn't change the outcome, but the development still added to the unrest over a long, contentious tally of ballots.

With 99.99% of votes counted, Morales had 47.07% to 36.51% for former President Carlos Mesa, who finished second in the nine-candidate field. That gave Morales a 10.56-point lead, a little more than a half point over the threshold he needed to win an outright victory and avoid a second-round ballot in December probably against a united opposition.

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"We won in the first round," Morales declared at news conference early in the day, after he first edged over the threshold during the night. The president, the region's longest-serving leader who is seeking a fourth consecutive term, said he was bolstered by the rural vote.

Morales later backtracked a bit, saying he would be open to a runoff if he fell short of the 10-point lead when official totals were announced.

A communique issued by Colombia's foreign ministry on behalf of the U.S., Brazil and Argentina said the governments of the four nations "will only recognize results that reflect the will of the Bolivian people."

Supporters and detractors of Bolivia's President and current candidate Evo Morales confront each other in Santa Cruz de la Sierra, Bolivia, October 24, 2019. Reuters

The European Union took a similar stand, saying it backed a call by the Organization of American States for a second-round election that could help Bolivia regain its footing after days of sometimes violent protests by opposition supporters angered by the slow vote count and an unexplained 24-hour halt in the release of results.

"The European Union shares the OAS' assessment that the best option would be to make a runoff to restore trust and ensure full respect for the democratic elections of the Bolivian people," the EU said in a statement that also called for the parties to refrain from further violence.

There was no comment from Morales about the outsiders' questions on the fairness of the election's opening round.

Opposition leaders were united in rejecting Morales' victory claim as the president's supporters were out celebrating. Analysts have said a united opposition might stand a chance in a second round of defeating Morales, a leftist former coca-growers union leader who has governed the Andean nation for 14 years.

Flanked by other opposition leaders, Mesa read a statement calling for "citizens and social groups to remain peacefully mobilized until they obtain respect for the will of the people."

Morales, in turn, urged his supporters to defend his win and denied electoral fraud, demanding his detractors show proof.

"We are at the start of a crisis that could affect the social, political and economic stability of the country," said political analyst Jorge Dulón at Bolivian Catholic University.

The Andean nation has been on a knife-edge since the bitterly disputed vote.

Opposition backers have stage rowdy protests since Monday and burned Supreme Electoral Tribunal offices in three cities. The opposition bastion of Santa Cruz has seen two days of a partial strike "in defense of the vote and democracy."

On Thursday, Morales supporters announced marches in the coca-growing region of Chapare, a bastion of support for the president.

International vote monitors have questioned the early daylong gap in reporting results before a sudden spurt in Morales' vote percentage. An OAS observer mission released a statement expressing its "concern and surprise over the drastic change and difficult to justify tendency in the preliminary results."

Morales had repeatedly said since late Sunday that he won the vote outright and that his opponents are conspiring to oust him.

Suspicions of electoral fraud rose when officials abruptly stopped releasing results from the quick count of votes hours after the polls closed Sunday. Morales was leading at the time, but also falling several percentage points short of the 10-point edge he needed to avoid being forced into a runoff for the first time in his four election contests.

Twenty-four hours later, the electoral body suddenly released an updated figure, with 95% of votes counted, showing Morales just 0.7 percentage point short of the 10-point advantage. Since then, results have slowly been updated.

Morales, 59, a native Aymara from Bolivia's highlands, became the country' first indigenous president in 2006 and easily won the two following elections amid more than a decade of a commodities-fed economic boom in South America's poorest country. He paved roads, sent Bolivia's first satellite to space and curbed inflation.

But he has faced growing dissatisfaction, especially over his refusal to accept the results of a 2016 referendum to keep limits on presidential terms. The country's top court, considered by critics as friendly to the president, ruled that limits would violate Morales' political rights as a citizen.