George Michael has pneumonia and has postponed upcoming concerts, the British singer’s website said Wednesday, with Austrian television reporting he was being treated in a Vienna hospital.

A statement posted late Wednesday on http://www.georgemichael.com/ said Michael, 48, had been “diagnosed with pneumonia. He is currently receiving treatment.”

Concerts on this coming Saturday and Sunday in Cardiff, Wales have been postponed, following the cancellation of earlier gigs in Vienna on Monday and in Strasbourg, France on Wednesday.

Austrian channel ORF reported that the singer was also suffering from heart problems but the statement gave no further details, and contacted by AFP, the Vienna hospital where he was reported to be being treated declined to comment.

The singer — who first found fame in 1980s pop group Wham! and has gone on to sell more than 100 million records worldwide – has performed around 45 shows to date as part of his “Symphonica – The Orchestral Tour” that began in August.