Spanish singer Sergio Blanco has died at the age of 66.

The musician passed away at a hospital in Madrid on Sunday (15Feb15) after a mystery two-year illness forced him to retire from the stage.

His daughter, Allende, tells Spanish news agency Efe, "He was a marvelous person, and I have no words to say how my father was, he had an incredible vital force."

Blanco joined his future wife Estibaliz Uranga's group Voces y Guitarras in 1968 and the couple later teamed up in the band Mocedades.

They quit in 1972 and launched themselves as a duo, Sergio y Estibaliz, finding fame with the success of their self-titled debut album.

They were selected to represent Spain at the 20th Eurovision Song Contest in Sweden in 1975, when their song Tu volveras placed 10th.

Sergio y Estibaliz's last project was released in 1992, before the husband and wife became part of the line up for the group El Consorcio, reuniting with Uranga's siblings and fellow former Mocendades members, Amaya and Inaki, with whom they released eight albums.