George Michael has pulled the plug on the rest of his tour as he battles "severe" pneumonia.

The singer, who is being treated in hospital in Vienna, Austria, was said today to be responding to treatment and "slowly improving".

But he has now been told by doctors to take "complete rest" and the remainder of his scheduled shows have been put on hold.

The star, who has been diagnosed with "community acquired pneumonia", was due to play UK shows on his Symphonica tour until the week before Christmas.

His publicist said: "He is receiving excellent medical care; he is responding to treatment and slowly improving."

Doctors said they could not estimate how long he would need to recover.

It is the latest medical setback during the tour, his first for three years after previously saying he was to quit playing live. Just a month ago he was forced to pull out of an appearance at the Royal Albert Hall due to a viral infection and high temperature.

Michael, 48, spent a month in prison for drug driving last year.

Specialists in Vienna, Dr Christoph Zielinski and Dr Thomas Staudinger, issued a statement today saying: "George Michael has severe community acquired pneumonia and is being treated as an inpatient. His condition has stabilised and he is responding to treatment.

"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. Besides medical treatment, complete rest and peace and quiet are mandatory."

Promoters are working to rearrange the postponed dates "at the earliest opportunity".

The tour began in Prague in August and has so far seen him play 45 shows in 35 cities.