NEW YORK, NY.- It was the third act of Giacomo Puccini’s “Tosca” at a theater in Seoul, and South Korean tenor Alfred Kim, responding to enthusiastic applause, was singing a rare encore of “E lucevan le stelle,” one of the opera’s most beloved arias.

Then the unexpected happened: Celebrated soprano Angela Gheorghiu, who was singing the title role in a performance Sunday, stormed onstage and demanded that he stop, according to local media reports and accounts by audience members.

“Excuse me,” she said, signaling to the orchestra to pause.

When the orchestra continued playing, she also refused to stop. “It’s a performance; it’s not a recital,” Gheorghiu said. “Respect the audience. Respect me.”

Gheorghiu, 59, a diva of the old school known for her preternatural voice and strong-willed demeanor, faced an immediate backlash.

She initially did not appear for a curtain call. But when she eventually emerged, she was booed, blowing a kiss as she exited the stage after only a few seconds. She was widely denounced by commentators and fans in South Korea. And the Sejong Center for the Performing Arts, where the performance took place, demanded an apology.

After days of criticism, Gheorghiu, who has long made clear her disdain for encores in opera, defended her actions.

Her managers released a statement Wednesday saying that she had been assured by the conductor, Jee Joong-bae, and the production team in Seoul that there would be no encores. She said she had declined a suggestion by Jee that she sing an encore “to maintain the integrity of the performance.”

“Ms. Gheorghiu believes firmly that encores outside of a concert performance setting disrupt the narrative flow of opera,” the statement said.

(The performing arts center told The Korea Times that Gheorghiu had conveyed her desire for no encores, but that there was no binding agreement.)

Gheorghiu saw the encore by Kim, who was singing the role of Cavaradossi, Tosca’s lover, as a “personal affront given her strong convictions on this matter,” the statement said. Her representatives added that she had been subject to an “extraordinary level of abuse” online after the incident.

Gheorghiu has been accused of prima donna behavior before.

She once balked at wearing a blond wig while singing the part of Micaela in Franco Zeffirelli’s production of Georges Bizet’s “Carmen” during a Metropolitan Opera tour of Japan. That led Joseph Volpe, who was then the company’s general manager, to tell her that “the wig goes on, with or without you.”

In 2016, trouble erupted during a run of “Tosca” at the Vienna State Opera when Gheorghiu’s co-star, acclaimed tenor Jonas Kaufmann, sang an encore of the same aria she interrupted Sunday, “E lucevan le stelle.”

Gheorghiu conspicuously missed her entrance, leaving Kaufmann awkwardly alone onstage. He improvised, singing “Non abbiamo il soprano” (“We don’t have a soprano”) in Puccini-like strains. The opera eventually began again, and Gheorghiu entered.

The Vienna State Opera said at the time that it did not appear to be an intentional slight, and that Gheorghiu had returned to her dressing room when she learned Kaufmann was repeating the aria.

Tosca is a signature role for Gheorghiu, who was born to a dressmaker and a train operator in Adjud, Romania. She rose to the heights of the opera world in the 1990s, praised for her flexible and free voice. But she has been less of a presence on the world’s top stages in recent years as her voice has faded somewhat.

In South Korea, where Gheorghiu’s Tosca had been heavily marketed — advertisements called her “the best Puccini specialist of our time” — the interruption received wide attention. She was denounced on social media for showing an “arrogant attitude,” and some patrons demanded refunds, according to The Korea Times.

The Seoul Metropolitan Opera, which is part of the Sejong Center for the Performing Arts and produced “Tosca,” apologized for the episode, vowing in a statement to “strongly protest” Gheorghiu’s behavior and “request an apology to the Korean audience.”

Gheorghiu stopped short of apologizing, saying in her statement that she “deeply regrets the circumstances” that led to the incident.

“Ms. Gheorghiu wishes to express her profound respect and love for Korean audiences,” the statement said, “with whom she has cherished a wonderful relationship for many years.”

This article originally appeared in The New York Times.