CARACAS — Lawmakers aligned with Venezuela’s repressive leader, Nicolás Maduro, began an attempt to consolidate his grip on the nation on Sunday by wresting control of the National Assembly, the last political institution still dominated by the opposition.
In a chaotic session in which security forces surrounded the National Assembly building, intimidating members of the opposition who tried to enter, supporters of Mr. Maduro blocked the re-election of Juan Guaidó, the opposition leader, as the body’s head, and named another legislator instead.
Members of the Venezuelan opposition immediately denounced the effort, calling it a “parliamentary coup d’état” and saying there had been no quorum to call the vote.
The move plunges the country’s already turbulent political situation further into chaos, raising questions about who controls the assembly and whether Mr. Guaidó can continue to assert that he is the Venezuela’s interim president, in a direct challenge to Mr. Maduro.
Mr. Guaidó positioned himself as head of a caretaker government a year ago, just two weeks after being elected head of the assembly. Standing in the streets of Caracas with hundreds of thousands of Venezuelans, Mr. Guaidó said then that Mr. Maduro’s 2018 election was fraudulent. Invoking an article of the Constitution that transfers power to the head of the assembly if the presidency becomes vacant, he claimed the country’s leadership.
That announcement last year was quickly recognized by dozens of foreign governments, including the United States, which backed him by imposing crippling sanctions on Mr. Maduro’s government.
To continue to claim the interim presidency, Mr. Guaidó needed to be re-elected as head of the assembly on Sunday, according to analysts in and outside the country.
His victory was expected, as the opposition controls the legislative body, but at the last minute, members of the National Guard prevented Mr. Guaidó from entering the assembly’s white-walled building. Inside, a member of Mr. Maduro’s party, Héctor Agüero, swore in Luis Parra as head of the assembly. There was no vote count.
Mr. Parra is a former member of the opposition who turned against Mr. Guaidó after Mr. Guaidó opened a corruption claim against him.
The United States immediately condemned the move.
On Twitter, Michael Kozak, acting assistant secretary for the Department of State’s Bureau of Western Hemisphere Affairs, said that Mr. Guaidó “remains Venezuela’s interim president under its constitution,” adding that Sunday’s “phony National Assembly session lacked a legal quorum.”
In recent weeks, the opposition and the United States government accused Mr. Maduro of trying to block Mr. Guaidó’s re-election by bribing and harassing lawmakers.
In December, Elliott Abrams, the United States special envoy to Venezuela, accused Mr. Maduro of trying to pay deputies up to $500,000 each to vote against Mr. Guaidó’s re-election.
In an interview just days after Christmas, Mr. Guaidó, 36, insisted that he had the votes for re-election. But he acknowledged that Mr. Maduro was unpredictable and that anything could happen. “There is no manual,” he said, “for battling a dictatorship.”
Ana Vanessa Herrero contributed reporting from Caracas.