ATHENS (REUTERS, AFP) - Greek singer Demis Roussos, 68, who sold more than 60 million records worldwide with a series of international hits in the 1970s and 1980s, died in Athens on Sunday after a long illness, reports said.

He was part of progressive rock group Aphrodite's Child but was best known for his solo hits, among them Forever And Ever, Mr Reason, Goodbye My Love Goodbye, Quand je t'aime and Happy To Be On An Island In The Sun.

His Aphrodite's Child bandmate Vangelis, in a statement quoted by the BBC, said: "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."

It was Roussos' melancholy face on 1970s and 1980s album covers that provided the most enduring image of him: a theatrical figure with a flowing dark beard, intense dark eyes and long hair thinning on top.

He carried his larger-than-life persona on stage with colourful clothing, and sustained it with a voice that belted out powerful operatic flourishes.

"Back in 75 I had five albums in the top 10. Simultaneously. And among them the number one album and the number one single," he said in an interview with The Guardian in 1999, referring to his success in Britain. "And my name was mentioned twice or three times in the Guinness Book of Records."

Roussos was born on June 15, 1946, and was raised in Alexandria, Egypt, by his Greek engineer father and his Egyptian mother of Italian heritage. The family moved to Greece during the Suez Crisis.

Though he had been singing since childhood, Roussos began his musical career at 17 playing guitar and bass in a band called The Idols, where he first met Vangelis.

During one of the group's performances, Roussos briefly replaced the lead singer and belted out his rendition of the American folk ballad House Of The Rising Sun.

The audience, according to Roussos' website, was instantly captivated by his voice.

He found fame in the 1970s after teaming up with Vangelis in Aphrodite's Child. He soon went solo and built a long career.

He was aboard a TWA flight when it was hijacked by men with Lebanese group Hezbollah on June 14, 1985.

In exchange for Roussos and the other hostages, Hezbollah demanded the release of 17 of its militants and Iraqi Islamic Daawa Party members, who were arrested in Kuwait in connection with attacks that killed six people in 1983.

Roussos, who spent his 39th birthday in captivity, was released four days into the ordeal. Most of the roughly 150 passengers were held for nearly two more weeks.

"They gave me a birthday cake and they gave me a guitar, to sing," Roussos told reporters at the time. "They have been very polite and very nice with us."

"Along with Nana Mouskouri, he is one of the two biggest Greek pop music artists. They are the two great voices that put Greece on the map," French-Greek television personality Nikos Aliagas said.

"We had known each other since I was a kid. He broke through borders and made his country proud."

Roussos had long struggled with his weight, but he later slimmed down and even penned a diet book called A Question Of Weight.

In subsequent years he suffered ill health that kept him chair-bound.

He recorded and toured until 2009, when he released his last album. One of his last public appearances was in Athens in 2013, when he received the Legion of Honour - France's highest distinction - for his life's work.

He leaves behind two children, Emily and Cyril, who are both musicians.

A public funeral is to take place on Friday at the First Cemetery of Athens, a resting place for many Greek politicians and cultural figures.