LONDON - Madonna and Elton John led tributes from around the world for British pop star George Michael, who died at his home near London on Sunday aged 53.
"Farewell my Friend! Another Great Artist leaves us. Can 2016 **** Off NOW?" Madonna wrote in a post on Instagram accompanied by a video of her presenting Michael with an award.
Elton John also published a picture of himself with Michael, saying: "I am in deep shock. I have lost a beloved friend - the kindest, most generous soul and a brilliant artist".
Michael shot to fame with the 1980s band Wham! and sold over 100 million albums in his career, winning two Grammies and three Brit awards.
Referring to him by his nickname "Yog" (Yours Only George), Wham! co-star Andrew Ridgeley said he was "heartbroken" by Michael's death.
Many reactions referred to the spate of music world deaths in 2016, starting with David Bowie in January.
Singers Prince and Leonard Cohen also died this year and Status Quo guitarist Rick Parfitt passed away on Saturday in a Spanish hospital.
"2016 - loss of another talented soul. All our love and sympathy to George Michael's family," the band Duran Duran, who were 1980s contemporaries of Wham!, said on their official Twitter account.
Spandau Ballet, a British band which formed in the late 1970s, wrote: "We are incredibly sad at the passing of our dear friend George Michael. A brilliant artist & great songwriter."
Newer pop stars also paid tribute to the influential London-born artist, who was planning to release a new album and a documentary next year.
"Oh God no... I love you George... Rest in peace," wrote pop star Robbie Williams, while fellow singer Pixie Lott paid tribute on Twitter to the "beautiful and talented" Michael.
In the United States, Recording Academy president Neil Portnow said he was "deeply saddened" by the loss.
"During an influential career that spanned nearly four decades, George became one of the most beloved pop craftsmen and respected entertainers," said Portnow, whose organisation awards the Grammies.
"From the enormous success he achieved with pop duo Wham! to his influential solo career, his extraordinary talent had a profound impact on countless entertainers worldwide, and his creative contributions will live on forever," he said.
Canadian musician Bryan Adams tweeted: "I can't believe it. Such an incredible singer and a lovely human being, far too young to leave us." US singer La Toya Jackson wrote: "You have given the world an amazing gift! What a talent! What a loss!".
Tributes came in from outside the music world too.
Football presenter and former England captain Gary Lineker tweeted: "No, not George Michael as well. Another musical great leaves us this year. 2016 can just sod off."
"Star Trek" actor George Takei referred to some of Michael's greatest hits in a tweet, writing: "Rest with the glittering stars, George Michael. You've found your Freedom, your Faith. It was your Last Christmas, and we shall miss you."
London Mayor Sadiq Khan said Michael "brought joy to millions of us" and British opposition Labour Party leader Jeremy Corbyn hailed Michael as a "strong supporter" of gay and workers' rights.
Following years of speculation about his sexuality, Michael came out as gay in 1998 after being arrested for committing a lewd act in the public toilet of a Los Angeles park.
The gay rights charity Stonewall said: "You inspired many and your music will live on in the hearts of the community. You will be sorely missed."