Robin Gibb of the pop group the Bee Gees is in a coma after suffering from pneumonia, his official website says.
The singer has been been battling colon cancer, which later spread to his liver.
"Sadly the reports are true that Robin has contracted pneumonia and is in a coma," the singer's website said.
"We are all hoping and praying that he will pull through."
The 62-year-old had been too ill to attend the London premiere of his first classical work on 11 April, the BBC reports.
Britain's Sun newspaper said his family was keeping a bedside vigil at the hospital in London.
The Bee Gees - formed by Gibb and his brothers Maurice and Barry - are one of the most successful bands in pop history, with hits like Massachusetts and Night Fever.
They also wrote dozens of songs for other artists.
Robin Gibb has also released several solo records, although only 2003's Magnet charted in the UK
The Bee Gees disbanded after Maurice Gibb's death in 2003, which was caused by complications from a twisted intestine.