Roxy Music frontman Bryan Ferry was admitted to hospital on Tuesday and is said to be "seriously ill".
The 65-year-old was due to make an appearance at a 2012 Olympics event, but pulled out after saying he had been feeling unwell for some time.
There were initially fears that the pop legend had suffered a heart attack, but a spokesman for the star dispelled the rumours.
"Bryan has been feeling rough for some time and he felt even worse today. So, he thought it was best for the doctors to look into it," said a friend of the 65-year-old.
"We're all obviously very concerned for him."
Bryan has a series of concerts booked throughout the summer, but it is not yet sure if these dates will be affected.
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