"A race with time" is how the singer's family described his health situation, reported the newspaper Correio da Manha. The family has otherwise refused comment.

According to media reports, 27-year-old Salvador Sobral is at the intensive care unit of the Santa Cruz hospital in Lisbon. His condition is described as "stable, but critical." Suffering from a serious heart ailment, Sobral has been waiting for a donor heart.

The scion of a family of nobility and former student of psychology won this year's Eurovision Song Contest (ESC) in Kyiv on May 13 with the gentle jazz ballad "Amar Pelos Dois" (Love for Two).

Read more: Opinion: And the Eurovision winner is - the music

After his Eurovision triumph, Salvador Sobral gave numerous concerts but cancelled a number of appearances in late August due to his deteriorating health.

Salvador Sobral enchanted Europe with his song about a broken heart

Sobral bade a tearful farewell to his audience on September 8, titling his concert "Ate já" (See You Soon). The singer announced in a pre-concert television appearance that he would have to take a break due to his health problems. "How long an interruption it will be, nobody in this world knows. Maybe God, maybe an E.T." he said.

In a video for his fans on Facebook from early September, Sobral said it was "time to donate my body to science."

Highly criticized after his failure on a Portuguese television casting show in 2008, Sobral was sent to the 2017 ESC. Lacking glamour and with a slightly quirky stage demeanor, he was an early favorite and cruised to victory with a simple and intimate jazz ballad written by his sister, Luisa Sobral.

The win made him an a much loved and recognized artist and a national hero in Portugal.