Election officials said Maduro, who faced a stiff challenge from a united opposition, won 51 percent of the vote.
Venezuela announced that incumbent Nicolas Maduro had won presidential elections on Sunday, but the opposition said it was preparing to contest the results.
Elvis Amoroso, head of the CNE electoral commission, said Maduro secured a third six-year term with 51.2 percent of the vote. Opposition candidate Edmundo Gonzalez Urrutia, who had been leading the polls, received 44.2 percent, he said.
The electoral commission, controlled by Maduro's allies, did not immediately release the results from the tally of 30,000 polling stations across the country.
Opposition leaders had earlier said tallies collected from campaign center representatives showed Mr Gonzalez was leading Mr Maduro by a large margin.
Speaking shortly after the announcement, President Maduro called his re-election a victory for peace and stability, and reiterated his claim during the campaign that the voting system was transparent.
Maduro, 61, first came to power after his leader, socialist President Hugo Chavez, died of cancer in 2013.
The president has been accused of jailing critics and harassing the opposition and has failed to end a years-long economic crisis that has caused more than 7 million of Venezuela's 30 million people to leave the country.
The opposition campaigned on a promise to end the economic crisis, and exit polls suggested they had a good chance of defeating President Maduro.
Gonzalez replaced popular opposition leader Maria Corina Machado as the candidate after authorities loyal to Maduro barred her from the election.
Machado, who has been campaigning across the country for his surrogates, had urged voters late on Sunday to be “vigilant” at polling stations during “crucial hours” of vote counting amid fears of fraud.
Gonzalez received 70 percent of the vote, she said.
“We want the whole world to know that we won in every area, in every state in the country. We know what happened today. We have made sure that all information was collected and reported. This shows the results. It is irrefutable,” Corina Machado said at the rally.
Gonzalez also disputed the official results, telling supporters in Caracas that the government had “violated all the rules and norms and, as a result, we were denied access to most of the ballots.”
“Our struggle continues and we will not rest until the will of the Venezuelan people is respected,” Gonzalez said, but stressed he was not calling on his supporters to take to the streets and commit acts of violence.
'violation'
Sunday's election was the result of an agreement reached last year between the government and the opposition.
The agreement allowed the United States to temporarily ease sanctions imposed after Maduro's 2018 reelection, which was rejected by Western countries and dozens of Latin American nations as a sham election.
Sanctions were reinstated after Maduro violated the terms of the agreement, but Washington did not welcome the announced results.
U.S. Secretary of State Antony Blinken expressed concern over Maduro's declaration of victory and said the United States wanted the votes to be counted “fairly and transparently.”
“We have serious concerns that the results announced do not reflect the will and vote of the Venezuelan people,” he said.
The EU and several member states have also raised concerns about the transparency of the vote.
Analysts and leaders across the Americas have expressed skepticism, but some have voiced support for Maduro.
“Everything we’ve seen so far indicates that the government’s achievements are just manufactured,” Phil Gunson, senior Venezuela analyst at the International Crisis Group, told Al Jazeera.
He claimed that the results released by the government-controlled electoral authorities did not match the actual number of votes.
“The results that the opposition claims to be correct are very consistent with what has been seen in the polls over the past few months,” Gunson said. “All the partial results we've seen so far show the opposition winning roughly three-fifths of the vote.”
Francisco Rodriguez, a professor of international public policy at the University of Denver, said Venezuela's opposition must document any alleged wrongdoing and make public the results of its investigations.
“I have to publish… [the individual] “They should check the results from the polling stations and show how they contradict what the electoral authorities are showing,” Rodriguez told Al Jazeera on Monday morning.
Costa Rican President Rodrigo Chavez and Peruvian Foreign Minister Javier González Olaechea both rejected the official election results as fraudulent, and Lima recalled its ambassador from Caracas, citing “violation of the will of the people.”
Chilean President Gabriel Boric described the results as “hard to believe” while Uruguayan President Luis Lacalle Pou said the “tally was clearly flawed.”
But Maduro had the backing of allies in Bolivia, Honduras and Cuba.
Cuban President Miguel Diaz-Canel said Maduro had “clearly and unequivocally defeated the pro-imperialist opposition.”
China's Foreign Ministry also congratulated President Maduro on his reelection.
