LONDON: Whitney Houston has sparked fresh fears for her health after appearing at a concert in Australia looking exhausted as she struggled through her set. The singer, who kicked off her first world tour in a decade at the end of last year (Dec09), became the subject of a National Enquirer report last week (ends19Feb10), alleging Houston has been in a fragile state. Houston's representative blasted the claims, insisting rumours she is battling a mystery illness are "ridiculous". But the R&B superstar's troubled performance at the Brisbane Entertainment Centre on Monday (22Feb10) has done little to dampen the claims - after appearing to be out of breath moments into the gig, the first on the Australian leg of her Nothing But Love tour. Local reports state Houston only sang two songs before she was forced to take a break. She resumed the concert and sang six more songs, reportedly coughing through the tracks, before leaving the stage and calling on her brother Gary to take over the microphone and sing. When Houston reappeared onstage, she sat through some acoustic versions of her hits and ended the show with a below-par performance of her classic hit I Will Always Love You, pausing midway through the song to take sips of water. One disappointed concert-goer tells the Courier-Mail, "She was not fit to perform. She seemed to be on another planet, and the concert was laughable. When the back up singer's performance is the stand out for the night you know something is wrong." Houston is next due to appear at the Acer Arena in Sydney on Wednesday (24Feb10).