Belgian Gerard Mortier, the avant-garde artistic director of Madrid's Teatro Real and other European opera houses over the last 30 years, has died aged 70 after battling cancer.
Mortier, known for his risk-taking approach to scene work and keen interest in 20th-century opera, commissioned an adaptation of gay cowboy epic "Brokeback Mountain" for Teatro Real, which he headed until September last year.
US composer Charles Wuorinen took six years to complete the "Brokeback Mountain" opera, and a clearly ailing Mortier attended its premiere in January.
He died on Saturday at his home in Brussels, Teatro Real said in a statement, expressing its "deep sadness".
Belgian Prime Minister Elio Di Rupo paid tribute to his countryman, tweeting: "Our country has lost a visionary and generous figure," while Culture Minister Fadila Laanan said Mortier's "often non-conformist choices, his audacious programming built his international renown".
Cannes Film Festival president Gilles Jacob hailed Mortier as a "great non-conformist and innovative opera director", and prominent British music critic Norman Lebrecht called him "brilliant and infuriating".
The son of a Flemish baker, he was born in Ghent on November 25, 1943. He studied in Germany and gained fame as general director of Belgium's Rola Theatre of the Mint for three years from 1981.
Mortier's success later caught the attention of the prestigious Salzburg Festival which he headed from 1991 to 2001.
When he took over the Paris Opera from 2004 to 2008, his innovative productions sometimes shook up the audience, such as the time a spectator at Gluck's "Iphigenia" opera cried out: "Mortier to the stake!"
"I have my detractors... but I also have a very loyal public of aficionados," Mortier said upon leaving Paris in 2009.
The Paris Opera expressed "great sadness" over the death of its one-time controversial director on Sunday, saying it will dedicate its production of Wagner's "Tristan and Isolde" to him in April.
And France's President Francois Hollande hailed Mortier as a fighter "for culture in Europe. His originality and talent will be missed," a French presidency statement said.
In Madrid, Mortier won accolades for productions at Teatro Real of Mozart's "Cosi fan Tutte" directed by Austrian filmmaker Michael Haneke and Philip Glass's "A Perfect American"
Teatro Real said on Sunday the flags outside the theatre would be at half-mast for its former director.
The theatre would also dedicate Sunday afternoon's performance of Gluck's "Alceste" to Mortier, with a moment of silence to be held in his memory.
A tribute to Mortier is also being planned which will include young people, "thus representing his legacy as a great promoter of opera as an avant-garde art," Teatro Real said.
Mortier's funeral "will be strictly private, as he wished", it added in a statement.