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.
Roussos was as famous for his outfits as his music
He had been in the private hospital with an undisclosed illness for some time.
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."
The singer was born Artemios Ventouris Roussos in Alexandria, Egypt, in 1946, to a Greek father and Egyptian mother of Italian origin.
He was raised there until his parents moved to Greece in the early 60s after losing their possessions during the Suez Crisis.
Roussos began his music career at 17, when he joined the a band called The Idols, where he met his future Aphrodite's Child bandmate Vangelis.
Aphrodite's Child produced three albums including It's Five O'Clock and The Apocalypse of St John, and enjoyed huge success in Europe in the late 1960s, especially France.
Roussos went on to enjoy a successful solo career, topping the charts in several countries with Forever And Ever in 1973, before doing the same in the UK in 1976.
The 1970s were a prolific time for the singer who talked about his UK success during that time in an interview with The Guardian in 1999.
"This country was one of my most important territories," said Roussos.
"Back in '75 I had five albums in the top 10. Simultaneously. And among them the number one album and the number one single. And my name was mentioned twice or three times in the Guinness Book of Records."
He continued: "In 1975 I had the award for the top male artist, the award for top single, the award for top album. The Abba and me we took everything. Hahahaha!"
Other solo hits include My Friend the Wind, My Reason, Someday Somewhere and Happy To Be On An Island In The Sun.
Roussos' fondness for kaftans saw him dubbed "the Kaftan King" and he often wore them for his performances on shows such as Top of the Pops.
He was also famous for his vocal adaptation of the score from the 1981 film Chariots of Fire, which had been composed by Vangelis.
In 1978 he decided to keep a lower profile and moved to Malibu Beach in the US.
On 14 June, 1985, Roussos boarded TWA Flight 847 from Athens to Rome - and found himself at the mercy of the Lebanese militant group Hezbollah, who hijacked the plane.
The men, who had smuggled a pistol and grenades through airport security, held the passengers at gunpoint.
The militant group demanded the release of 17 members of Hezbollah and the Iraqi Islamic Daawa Party, who had been detained in Kuwait for attacks that killed six people in 1983.
Roussos spent his 39th birthday in captivity, before being released in Beirut on 18 June - but most of the remaining 153 passengers spent 17 days on the plane.
Speaking to the Reuters news agency at the time, the singer said he had been "treated quite well".
"They gave me a birthday cake and they gave me a guitar, to sing," he said. "They have been very polite and very nice with us."
Return to music
Over the years, his quote became misinterpreted and distorted. Some papers said he had serenaded the hijackers. Others claimed he had pledged allegiance to Hezbollah.
Roussos, who rarely spoke about the incident, admitted he was riled by the exaggerations in an interview with Australia's Daily Telegraph in 2006.
"It is not every day that a pop superstar gets involved with terrorism as a victim, so the press takes advantage of that to say things they think are funny.
"I would like to see the journalist [who first reported the claim] in front of gunpoint like I was. Believe me, if he was there he would be so scared he wouldn't care about writing such stupidities like that.''
The experience changed his life and afterwards he decided the best way he could help others and promote understanding in the world was by returning to music.
He released his album The Story of Demis Roussos not long after.
ROUSSOS, Demis (Artemios Ventouris Roussos)
Born: 6/15/1947, Alexandria, Egypt
Died: 1/25/2015, Athens, Greece
Demis Roussos’ western – singer:
The Man from Cher (TV) – 1969 [member of the singing group Aphrodite’s Child]