Venezuelan security forces fired tear gas and rubber bullets Monday at protesters challenging the reelection victory claimed by President Nicolas Maduro but disputed by the opposition and questioned abroad.
Thousands of people flooded the streets of several neighborhoods of the capital, chanting "Freedom, freedom!" and "This government is going to fall!"
Some ripped Maduro campaign posters from street posts and burned them.
Maduro, 61, attended a meeting Monday at which the National Electoral Council (CNE) certified his reelection to a third six-year term until 2031.
He dismissed international criticism and doubts about the result of Sunday's voting, claiming Venezuela was the target of an attempted "coup d'etat" of a "fascist and counter-revolutionary" nature.
But opposition leader Maria Corina Machado later told reporters that a review of voting records available so far clearly showed that the next president "will be Edmundo Gonzalez Urrutia," who took her place on the ballot after she was barred by Maduro-aligned courts.
The records showed a "mathematically irreversible" lead for Gonzalez Urrutia, she said, with 6.27 million votes to only 2.75 million for Maduro.
The elections were held amid widespread fears of fraud by the government and a campaign tainted by accusations of political intimidation.
In the early hours of Monday, the CNE said Maduro had won 51.2% of votes cast compared to 44.2% for Gonzalez Urrutia.
The opposition cried foul, prompting Attorney General Tarek William Saab to link Machado to an alleged cyber "attack" seeking to "adulterate" the results.
The outcome sparked concern and calls for a "transparent" process from the United Nations, United States, European Union and several countries in Latin America.
Allies including China, Russia and Cuba congratulated Maduro.
Gonzalez Urrutia, a 74-year-old former diplomat, on Monday acknowledged the deep discontent in society with the CNE results and vowed that "we will fight for our liberty."
Machado assured Venezuelans that "the leaders of the world" are validating the results, and called families to turn out Tuesday for "popular assemblies" nationwide to show support for a peaceful transition of power.
Nine Latin American countries called in a joint statement Monday for a "complete review of the results with the presence of independent electoral observers."
Brazil and Colombia also urged a review of the numbers while Chile's president said the outcome was "hard to believe."
Peru recalled its ambassador and Panama said it was suspending relations with Venezuela.
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