The government claimed a turnout of nearly 8.1 million voters, or 41.5 percent — a figure the opposition, which boycotted the vote, called a fraud. The candidates for the new assembly were all government backers, including Maduro's wife and son. Opponents estimated the public lack of enthusiasm was so great that turnout had risen only to 12.4 percent.
"Venezuela has screamed with its silence," said Julio Borges, head of the National Assembly.
Reaction in Venezuela to creation of a super congress
The results unfolded on a deadly day in which the Maduro government showed zero tolerance toward pro-democracy protests, with shock troops firing volleys of tear gas and storming squares in the capital and beyond. Those citizens who did vote came under the watchful gaze of 326,000 national guards and police.
Late Sunday, the government extended voting hours, claiming large numbers of people still at polling stations. But at least 10 stations in the relatively more pro-government western swath of Caracas were virtually empty hours before voting was scheduled to end at 6 p.m. By midnight, Maduro was leading a triumphant rally in Plaza Bolivar in the city's center.
The attorney general's office, which broke with the government, declared 10 deaths Sunday, while the opposition said at least 16 had died in street clashes. A government official insisted that "not even one" death had occurred.
The election represents a direct challenge to the Trump administration, which called on Maduro, the anointed successor of late leftist firebrand Hugo Chávez, to cancel the vote.
Washington already has targeted the assets of top Venezuelan officials. The administration's options now range from more individual sanctions to penalties on oil trade with Venezuela that could further damage the country's devastated economy and at least temporarily increase the price of gas in the United States.
"We will continue to take strong and swift actions against the architects of authoritarianism in Venezuela, including those who participate in the National Constituent Assembly as a result of today's flawed election," U.S. State Department spokesman Heather Nauert said in a statement. "Nearly 234 years to the day after the birth of Simon Bolivar, who fought for the freedom of the people of Venezuela, President Nicolas Maduro has cast aside the voices and aspirations of the Venezuelan people."
On Sunday, members of the opposition set up barricades in parts of the capital and elsewhere and attempted to stage protests. But the government responded with extraordinary force.
In a scene repeated at various spots in the capital, a cluster of peaceful demonstrators were chanting for democracy and waving the yellow, blue and red Venezuelan flag in the city's Plaza Francia when riot troops suddenly materialized. They fired tear gas, sending demonstrators fleeing for cover.
"Today we protest for the freedom of the country, for the political prisoners, for the fallen, for the people who've died looking for a better future. . . . There are not enough people here because of fear," said a thin young man who broke away and ran as government forces took the square. Later, clusters of demonstrators returned, only to be chased again by troops.
A radical faction of government opponents — known as the Resistance — also used force. Around noon in the city's east, a protester in his 20s placed what appeared to be explosives inside a bag lying on the street. Five minutes later, as troops passed by in a motorcade, the bag detonated, throwing at least two of the men to the ground.
A pro-government candidate was killed in the interior state of Bolivar, according to the attorney general's office.
In Caracas, voting began at 6 a.m. amid the squawk of macaws. According to polling from the Datanalisis firm, 72 percent of the population is against a new Constituent Assembly.
The nation's 2.8 million state workers risked losing their jobs if they did not vote. Poor residents were warned that they could lose access to food baskets and government housing for failing to turn out for the election.
"To be honest, I'm voting because I'm afraid of losing my benefits," said Betty, 60, who lives in public housing and was too scared to give her last name. "The government gave me my house, and I don't want to lose it. I'm surviving because of government programs."
On San Martín Avenue, just a few blocks from the presidential palace, there were a few people voting at a public school, with 10 waiting in line. Some wore pro-government T-shirts.
Around 3:45 p.m., the opposition claimed only 1.5 million eligible voters — less than 7 percent of the electorate — had turned out. An unofficial opposition ballot held on July 16 had drawn nearly 7.6 million voters, and its results rejected Sunday's election.
Ramón Reyes works for the public TV station Televen. Many Chávez supporters — known as Chávistas — have turned against Maduro, but others turned out Sunday in support.
"As a citizen and Chávista, this is my responsibility," Reyes said. "I always voted for Chávez and the ruling party."
Other Chávistas said they have had enough.
"Everything has changed, everything," said Angely Verde, a 28-year-old former state worker who turned out for a protest. "This is not where I grew up. I can't recognize anything I'm seeing. It's so sad. Seeing other people who still have faith is what gives you energy and strength to go on."
Maduro has pitched the new legislature as the cornerstone of a socialist dream. Some candidates are former government officials, but many are government supporters from poor neighborhoods. The 545-seat body, Maduro says, will shift power away from traditional politicians and institutions toward socialist activists and slums — a move that critics say will sideline the opposition, benefit those who rely on government patronage and increase official control.
Maduro cast his ballot in front of national TV cameras with his "fatherland card" — which voters were required to use to prove their participation and ensure future government benefits. Suggesting systemic errors, the screen read, "This person doesn't exist or was annulled" before the camera immediately changed focus.
Later, Maduro claimed a success.
"It was and still is a successful day with great popular participation," he insisted on television. "The oligarchy doesn't have its eyes or ears on the people, and it never has. We don't care about the opinion of the oligarchy."
Officials and journalists from the pro-government station Telesur tweeted photos of lines at voting centers. Early Sunday, reports surfaced of violent confrontations between government forces and residents in western Caracas and the suburbs. On Saturday night, public security forces conducted raids in the center of the city and shot two young men in the state of Merida.
The decision to hold the vote appeared set to prolong and deepen the suffering of the people of Venezuela, where hyperinflation and scarcities have sent poverty soaring, crippled medical care and increased hunger. A tube of toothpaste now costs more than one day's salary at the minimum wage.
The government, meanwhile, was bracing for further international isolation. Thirteen nations from the Organization of American States had urged Maduro to cancel the vote.
On Twitter, Nikki Haley, the U.S. ambassador to the United Nations, wrote: "Maduro's sham election is another step toward dictatorship. We won't accept an illegit govt. The Venezuelan ppl & democracy will prevail."
Colombian President Juan Manuel Santos said Friday that his country would not recognize Sunday's vote. Mexico and Panama said they would collaborate with U.S. sanctions. In Europe, Spain urged the European Union to explore "individual and selective sanctions."
It left Venezuela with a dwindling roster of allies — chiefly Cuba, Russia and China.
Meanwhile, Delta Air Lines and Colombia's Avianca suspended service last week to Venezuela, citing security concerns.
Diosdado Cabello, one of Maduro's top lieutenants, said on national television that the candidates chosen Sunday would quickly replace elected legislators in the Federal Legislative Palace, the building in Caracas where the National Assembly meets. That prompted vows of large protests from the opposition.
However, after failing to muster massive crowds in the streets in recent days, the opposition appeared increasingly reliant on international pressure to curb what it called a power grab by the Maduro government. "Maduro is isolating us from the world and transforming our country into an island, like Cuba," Borges, the National Assembly leader, said.
For the opposition, which has portrayed the vote as the "zero hour" for Venezuela's democracy, the challenge is to find a way to reinvigorate an exhausted resistance. After four months of street protests in which thousands have been detained, the question is whether it can find new momentum.
In a sense, the new Constituent Assembly also poses risks for Maduro. The body will be all-powerful; in theory, its authority will be even greater than the president's. One scenario is that Maduro's wife or son will be installed as its head and the assembly will find a way to protect his grip on power.
The socialist government already controls the Supreme Court, which in March nullified the authority of the democratically elected National Assembly.
But the new body could also serve as the battlefield for a game of thrones among Maduro's inner circle. Speculation is particularly rife that Cabello may be gunning for the Constituent Assembly's top job, which he could potentially use to build his own power base.
"Inside the ruling party, different economic interests are at play, and they're waiting to see how the fight will end," said Félix Seijas Rodríguez, a Caracas-based pollster and political analyst.
"The internal fight has always existed," he continued. "The U.S. is waiting to see who will have control over the Constituent Assembly, either Diosdado or Maduro through his wife or [former minister] Delcy Rodríguez."
Mariana Zuñiga and Rachelle Krygier in Caracas and Carol Morello in Washington contributed to this report.