Brazilian singer Gal Costa, whose crystalline voice and transgressive sensuality made her the muse of the groundbreaking "Tropicalia" movement in the 1960s, died Wednesday, her public relations agency said. She was 77.

With her mane of brown curls and seductive smile, Costa sang with some of the biggest names on Brazil's booming popular music scene in the 1960s and immortalized many of their songs, including by Tom Jobim, Chico Buarque, Milton Nascimento and her close friend Caetano Veloso.

"Unfortunately, we confirm" that Costa died, a spokeswoman for Costa's PR firm told AFP, saying she could not give further details.

Costa, who lived in Sao Paulo, had recently canceled a concert at the city's Primavera Sound music festival on doctors' advice, after having surgery in September to remove a nodule from her right nasal cavity, according to Brazilian media.

But she had been expected to return to the stage, and her website listed her next performance as a concert in Sao Paulo on December 17.

News of her death brought an emotional outpouring in Brazil, including from some of the biggest names in music.

"I'm very sad and shaken by the death of my 'sister' @GalCosta," tweeted famed singer-songwriter and former culture minister Gilberto Gil.

Brazilian president-elect Luiz Inacio Lula da Silva posted a picture of himself embracing Costa on Instagram.

She was "one of the best singers in the world, one of our foremost artists who brought the name and sounds of Brazil to the entire planet," he wrote.

"The country... lost one of its great voices today."

Costa is survived by her 16-year-old adopted son, her agency said.