Protests began after the election board declared on Monday that Maduro had won a third term with 51% of votes to extend his "Chavista" movement’s quarter-century rule.
The opposition, which considers the election body in the pockets of a dictatorial government, said the 73% of vote tallies to which it has access showed its candidate Edmundo Gonzalez had more than twice as many votes as Maduro.
Many Venezuelans staged "cacerolazos", a traditional Latin American protest where people bang pots and pans in anger.
Some blocked roads, lit fires and threw petrol bombs at police as protests proliferated, including near the Miraflores presidential palace in Caracas.
"We are tired of this government, we want a change. We want to be free in Venezuela. We want our families to return here," said one masked protester, referring to the exodus of about a third of Venezuelans in recent years.
"I’ll fight for my country’s democracy. They stole the election from us," said another.
A local monitoring group, the Venezuelan Conflict Observatory, said it had registered 187 protests in 20 states by 6 p.m. on Monday with "numerous acts of repression and violence" carried out by paramilitary groups and security forces.
DEATHS
At least two people were killed in connection with the vote count or protests, one in the border state of Tachira and another in Maracay.
Maduro, a 61-year-old former union leader and foreign minister, won election after Chavez’s death in 2013 and was re-elected in 2018. The opposition said both votes were rigged.
He has presided over an economic collapse, mass migration, and deteriorating relations with the West including U.S. and EU sanctions that have crippled an already struggling oil industry.
His Defence Minister Vladimir Padrino warned against allowing a repeat of the "terrible situations of 2014, 2017 and 2019" when waves of anti-government protests led to hundreds of deaths and failed to dislodge Maduro.
Independent pollsters called Maduro’s victory implausible, while governments in Washington and around Latin America questioned the results and urged a full tabulation of votes.
"Not even (Maduro) believes the electoral scam he is celebrating," said Argentina’s President Javier Milei.
Peru ordered Venezuelan diplomats to leave within 72 hours, citing "serious and arbitrary decisions made today by the Venezuelan regime."
But in a familiar global division, allies including Russia, China and leftist-led Latin American nations backed Maduro.
"China will, as always, firmly support Venezuela’s efforts to safeguard national sovereignty, national dignity and social stability, and firmly support Venezuela’s just cause of opposing external interference," President Xi Jinping said in a message of congratulation.
Venezuelan opposition leader Maria Corina Machado, who was barred from running in the poll but has spearheaded the campaign for Gonzalez, called for marches on Tuesday.
"My dear Venezuelans, tomorrow we meet; as a family, organized, demonstrating the determination we have to make every vote count and defend the truth," she said.
The government is also planning pro-Maduro rallies, with many Venezuelans fearing another bout of violence and bloodshed similar to others in its turbulent recent history.
