LONDON -- George Michael has postponed all his remaining 2011 tour dates as he recovers from pneumonia, the singer's publicist said Friday.

Michael was hospitalized in Vienna, Austria earlier this week. A statement from publicist Connie Filippello said the 48-year-old former Wham! singer "is responding to treatment and slowly improving."

Michael "is ill with pneumonia and any other speculation regarding his illness is unfounded and untrue," the statement said.

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 gained mega-stardom in his early 20s as half of Wham! and went on to a successful solo career. His first solo album, 1987's "Faith," sold 20 million copies.

Michael had played 45 dates on his "Symphonica" European tour before falling ill.

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  • George Michael

    Singer George Michael poses at home with his cat after losing his voice and being forced to cancel a number of live shows in 1980, London. (Photo by Dave Hogan/Getty Images)

  • George Michael

    Picture of singer George Michael taken September 1997. Police in Beverly Hills have arrested a man who gave his name as George Michael for 'disorderly conduct'.The man, who gave his occupation as singer, was booked under the name Georgios Panayiotou - the former Wham star's real name - it was confirmed. (Photo credit should read JOHNNY EGGITT/AFP/Getty Images)

  • George Michael

    Singer George Michael performs on stage as part of the Net Aid concert on 9th October, 1999 at Wembley, London. (Photo by Dave Hogan/Getty Images)

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    LONDON - APORIL 19: British pop stars George Michael and Geri Halliwell attend the Capital Radio Awards at the Royal Lancaster Hotel on April 19, 2000 in London. (Photo by Dave Hogan/Getty Images)

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    LONDON - MARCH 24: Singer George Michael arrives at the Ivy Restuarant March 24, 2003 in London, England. (Photo by Bruno Vincent/Getty Images)

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    BERLIN - FEBRUARY 16: Singer George Michael arrives at the 'George Michael - A Different Story' World Premiere at Kino International during the 55th annual Berlinale International Film Festival on February 16, 2005 in Berlin, Germany. (Photo by Sean Gallup/Getty Images)

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    LONDON - JULY 02: Singer George Michael performs on stage at 'Live 8 London' in Hyde Park on July 2, 2005 in London, England. The free concert is one of ten simultaneous international gigs including Philadelphia, Berlin, Rome, Paris, Barrie, Tokyo, Cornwall, Moscow and Johannesburg. The concerts precede the G8 summit (July 6-8) to raising awareness for MAKEpovertyHISTORY. (Photo by MJ Kim/Getty Images)

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    LONDON - DECEMBER 05: (UK TABLOID NEWSPAPERS OUT) Singer George Michael (left) and Kenny Goss (right) arrive at the VIP preview screening of 'A Different Story', a documentary based on singer George Michael's life, at the Curzon Mayfair on December 5, 2005 in London, England. (Photo by Dave Hogan/Getty Images)

  • George Michael

    TOKYO, JAPAN - DECEMBER 15: British pop star George Michael attends the Japanese Premiere of his film 'A Different Story' on December 15, 2005 in Tokyo, Japan. The fim will open on December 23 in Japan. (Photo by Junko Kimura/Getty Images)

  • George Michael

    TOKYO, JAPAN - DECEMBER 15: British pop star George Michael and his partner Kenny Goss attend the Japanese Premiere of his film 'A Different Story' on December 15, 2005 in Tokyo, Japan. The fim will open on December 23 in Japan. (Photo by Junko Kimura/Getty Images)

  • George Michael

    LONDON - NOVEMBER 25: Singer George Michael performs at Earls Court on November 25, 2006 in London, England. (Photo by Getty Images)

  • George Michael

    LONDON - MAY 08: Former Wham! singer George Michael appears at Brent Magistrates Court on May 8, 2007 in London, England. Michael is charged with one count of being unfit to drive while under the influence of drugs after he was found slumped over the wheel of his car at traffic lights in north London on October 1, 2006 in London, England. He appears under his real name Georgios Kyriacos Panayiotou. The trial continues May 30-31 and June 8. (Photo by Peter Macdiarmid/Getty Images)

  • George Michael

    LONDON - MAY 08: Former Wham! singer George Michael leaves Brent Magistrates Court after pleading guilty to a charge of driving while unfit through drugs on May 8, 2007 in London. He appeared under his real name Georgios Kyriacos Panayiotou. (Photo by Peter Macdiarmid/Getty Images)

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    LONDON - JUNE 9: Singer George Michael performs the first concert at the newly rebuilt Wembley Stadium on June 9, 2007 in London. (Photo by Jim Dyson/Getty Images)

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    LONDON - JUNE 9: (UK TABLOID NEWSPAPERS OUT) George Michael performs at Wembley Stadium on June 9, 2007 in London, England. (Photo by Dave Hogan/Getty Images)

  • George Michael

    LONDON - JUNE 9: (UK TABLOID NEWSPAPERS OUT) George Michael performs at Wembley Stadium on June 9, 2007 in London, England. (Photo by Dave Hogan/Getty Images)

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    LONDON - NOVEMBER 18: (UK TABLOID NEWSPAPERS OUT) Musician George Michael (R) and his partner Kenny Goss arrive at the UK film premiere of 'Sleuth' at the Odeon West End on November 18, 2007 in London, England. (Photo by Dave Hogan/Getty Images)

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    SAN DIEGO - JUNE 17: Singer George Michael performs at the Sports Arena on June 17, 2008 in San Diego, California. (Photo by Kevin Winter/Getty Images)

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    NEW YORK - JULY 21: Singer George Michael performs at Madison Square Garden on July 21, 2008 in New York City. (Photo by Stephen Lovekin/Getty Images)

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    PERTH, AUSTRALIA - FEBRUARY 19: George Michael arrives by private jet at Perth's private jet base ahead of his national tour, which begins in Perth tomorrow night, on February 19, 2010 in Perth, Australia. (Photo by Paul Kane/Getty Images)

  • George Michael

    LONDON, ENGLAND - AUGUST 24: Singer George Michael (C) leaves Highbury Corner Magistrates Court surrounded by police on August 24, 2010 in London, England. Mr Michael pleaded guilty to driving under the influence of drugs and possessing cannabis after he crashed his car into a photo processing shop in London on July 4, 2010. (Photo by Peter Macdiarmid/Getty Images)

  • George Michael

    LONDON, ENGLAND - MAY 11: (UK TABLOID NEWSPAPERS OUT) George Michael attends a press conference to announce details of a new tour, at The Royal Opera House on May 11, 2011 in London, England. (Photo by Dave Hogan/Getty Images)

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    MILAN, ITALY - NOVEMBER 11: Singer George Michael performs at Mediolanum Forum on November 11, 2011 in Milan, Italy. (Photo by Vittorio Zunino Celotto/Getty Images)