Celebrities around the world are taking to social media to mourn the loss of George Michael, who died at 53 on Sunday.

Perhaps none of the tributes were more touching than that of Elton John, who called Michael “a beloved friend – the kindest, most generous soul and a brilliant artist.” The two singers scored a number 1 hit together in 1991 with a live cover of John’s “Don’t Let the Sun Go Down on Me.”

Another touching tribute came from Andrew Ridgeley, Michael’s former bandmate in the pop group Wham! The pair saw success in the 1980s with singles like “Wake Me Up Before You Go-Go,” “Last Christmas,” and “Club Tropicana.”

Read more of the tributes below: