Story highlights Wham! star George Michael is dead at the age of 53

is dead at the age of 53 Singer died at his home in England, family confirms

London (CNN) He was "the kindest, most generous soul and a brilliant artist," Elton John wrote on Instagram in one of the many tributes to pop star George Michael, who died at 53 on Christmas Day.

The singer is believed to have died from heart failure, his manager Michael Lippman said, according to the UK-based Press Association.

I am in deep shock. I have lost a beloved friend - the kindest, most generous soul and a brilliant artist. My heart goes out to his family and all of his fans. @GeorgeMichael #RIP A photo posted by Elton John (@eltonjohn) on Dec 25, 2016 at 3:24pm PST

Michael's death, which is being treated as "unexpected but not suspicious" by police, was also confirmed by the singer's family.

Fans have been leaving tributes outside Michael's London residence in Highgate.

"It is with great sadness that we can confirm our beloved son, brother and friend George passed away peacefully at home over the Christmas period," his family said in a statement.

In a career spanning four decades, the British pop singer sold over 100 million albums and had many chart-topping hits, including "Careless Whisper," "Faith," and "Father Figure."