The 48-year-old singer "is responding to treatment and slowly improving," according to a statement released Friday by his publicist Connie Filippello .
Michael "is ill with pneumonia and any other speculation regarding his illness is unfounded and untrue," the statement said.
Michael canceled shows in Vienna, Strasbourg, France and Cardiff, Wales, earlier this week after he was hospitalized in Vienna.
Two Austrian doctors treating Michael said he had "severe community acquired pneumonia," but "his condition has stabilized and he is responding to treatment." They said he needed time to regain his strength.
"From the current point of view, the time until recovery cannot be estimated, but he will not be able to perform the rest of the tour," Dr. Christoph Zielinski and Dr. Thomas Staudinger said in a statement. "Besides medical treatment, complete rest, and peace and quiet are mandatory."
The singer has postponed dates in Liverpool, Sheffield, Newcastle, Glasgow, Birmingham, Manchester and London. The statement said the concerts would be rescheduled. Michael had played 45 dates on his "Symphonica" European tour before falling ill.
The Associated Press contributed to this report.