LA PAZ, Bolivia -- Bolivian President Evo Morales accused his opponents Wednesday of trying to stage a coup against him amid protests over a disputed election that he claims he won outright, while a nearly finished but slow vote count had him teetering on the threshold between getting the win and having to go to a runoff.

The leftist leader needed a 10 percentage-point margin over his closest rival to avoid a December runoff in which he could risk being defeated by a united opposition in his bid for a fourth consecutive term in office.

The official vote count late Wednesday had him with a 9.87-point lead with just 2.36% of the votes from Sunday's election left to count. He led former President Carlos Mesa 46.7% to 36.83%.

The count had barely advanced since midafternoon, when authorities said the process had been hampered because of attacks on vote-count centres in three regions.

Mesa warned of fraud and international vote monitors expressed concern at an earlier unexplained daylong gap in reporting results before a sudden spurt in Morales' vote percentage. Opposition backers continued to stage rowdy protests since the vote, while Morales' backers staged a march in the capital to show their support for the president.

Morales, Bolivia's first indigenous president and the region's longest-ruling leader, repeated his claim that he won outright and said his opponents were conspiring to oust him.

"I want to denounce to the people and the world that a coup d'etat is underway," Morales said at a news conference at which he did not take any questions. "The right wing has prepared it with international support."

Morales did not specify where the alleged international support for the coup is coming from, but he regularly rails against U.S. imperialism in Latin America.

He cited the burning by protesters of electoral offices in two cities where votes are being tallied as proof of the coup. Protesters also burned ballots in a third city.

"We are waiting for a report from the Electoral Tribunal, although the TREP (a quick count) has already said that we won," the president said.

The tribunal's quick count webpage, whose results are not binding, showed Morales with a 10.1 percentage point lead over Mesa, with about 96% of polling place counts verified Wednesday.

"If there is anyone who breaks the constitutional order it is Evo Morales," Mesa said later in the day. "It's clear that there's a gigantic fraud going on."

Opposition leaders have called on Bolivians to defend "the citizen vote and democracy" in the streets against suspicions of fraud by Morales's party.

Suspicions of electoral fraud rose when officials abruptly stopped releasing results from the quick count of votes hours after the polls closed Sunday with Morales topping the eight other candidates, but also falling several percentage points short of the percentage needed to avoid the first runoff in his nearly 14 years in power.

Yet, the president claimed an outright victory late Sunday, telling supporters that the votes still to be counted -- largely from rural areas where he is most popular -- would be enough to give him an outright victory.

Twenty-four hours later, the body suddenly released an updated figure, with 95% of votes counted, showing Morales just 0.7 percentage point short of the 10-percentage point advantage needed to avoid a runoff.

That set off an uproar among the opposition and expressions of concern by international monitors.

The observer mission of the Organization of American States asked for explanations and the European Union and the U.N. expressed concern about the electoral process and called for calm. The United States and Brazil, among others, also expressed concerns.

Michael G. Kozak, acting U.S. assistant secretary of state for the Western Hemisphere, warned Wednesday that Bolivian authorities will be held accountable if the process isn't fair.

"I think you will see pretty strong response from the whole hemisphere, not just the U.S.," Kozak said during a House hearing.

In Caracas, Venezuela's socialist president, Nicolas Maduro, voiced support for his ally Morales.

"It is a coup d'etat foretold, sung and, one can say, defeated," he said.

The crisis was aggravated by the resignation of the vice-president electoral council, Antonio Costas, who said he disagreed with the decision to interrupt transmission of the vote count.

On Tuesday, the Andean nation saw a second night of violent protests in several cities. Then on Wednesday, a strike that mostly affected transportation erupted in Santa Cruz, the most populous eastern region and an opposition stronghold, while Morales supporters clashed with his foes in one of the city's slums.

Protesters in other regions announced that they would join to demand respect for the vote.