Greek singer Demis Roussos, who sold more than 60 million albums worldwide, has died aged 68, the Hygeia Hospital in Athens has confirmed to the BBC.
He was best known for his solo hits in the 1970s and 80s, including Forever and Ever, Goodbye and Quand je t'aime.
He was also a member of progressive rock group Aphrodite's Child.
Roussos was renowned for his off-screen role in Mike Leigh's 1977 TV play Abigail's party, having provided the party's soundtrack.
He had been in the private hospital with an undisclosed illness for some time.
His Aphrodite's Child bandmate Vangelis paid tribute in a statement that begins: "Demis my friend.
"I have just arrived in London and I've been told that you decide to take the long voyage, I'm shocked because I can't believe that this happened so soon.
"Nature gave you this magic voice of yours which made millions of people around the world very happy." Demis Roussos Roussos was as famous for his outfits as his music
He added: "As for me, I keep those special memories that we share together those early days and I wish you to be happy wherever you are."
He signed off with the words: "Goodbye my friend goodbye. Love Vangelis."
Greek singer Nana Mouskouri paid tribute on French radio RTL: "He had a superb voice, he travelled in the world ... he loved what he was doing.
"He was an artist, a friend. I hope he is in a better world."
Mike Porky Parry paid his own tribute to Demis Roussos is the early hours of this morning.You can see the 49 second clip here.Very, very hard to try to go asleep (as you've got to be up early in the morning) when that raving lunatic is creating such