Michael Jackson has died in hospital after suffering a suspected heart attack, website TMZ has reported.
Jackson, 50, suffered a heart attack just after 12.00pm local time (19.00pm GMT) and paramedics were unable to revive him, TMZ.comsaid.
When paramedics arrived at his house he was not breathing, a fire department captain told the LA Times newspaper.
Jackson was given CPR by fire department paramedics as he was taken to UCLA Medical Center where he was treated, the LA Times said.
Steve Hargrave, Sky's entertainment correspondent, said: "TMZ is a website which goes out of its way to get there first but many of their stories over the years have turned out to be true - particularly with stories from LA.
"You can only imagine the impact of this around the world."
Jackson's manager was not available for comment and officials at UCLA Medical Center could also not be reached.
Sky's US correspondent Greg Milam said: "Clearly he was very seriously ill - we can gather that from what his father and other family members said.
"One member of the family had told the TMZ website that Michael is in "really bad shape" and that the brothers were heading for the hospital.
"His father said he wasn't sure exactly what was wrong and was waiting to hear back.
"One can only imagine what it could be like for his family in such circumstances."
Jackson had been about to embark on a comeback, performing 50 concerts at London's O2 Arena.
The concerts had been due to start the concerts on July 13.
He had been rehearsing in the Los Angeles area for the London shows, which sold out within hours of within hours of going on sale in March.
Hargrave said: "We can't underestimate the effect this will have on Michael Jackson fans who have loved his music and career.
"They would have been assuming that in about three weeks time their idol would have been back on the stage perfoming his greatest hits. To suddenly find out this news will be devastating.
Phil Sutcliffe, from Mojo Magazine said: "He had the extraordinary effrontery to call himself the King of Pop, but that's actually what he was, and for a long, long time."
Jackson, 50, suffered a heart attack just after 12.00pm local time (19.00pm GMT) and paramedics were unable to revive him, TMZ.comsaid.
When paramedics arrived at his house he was not breathing, a fire department captain told the LA Times newspaper.
Jackson was given CPR by fire department paramedics as he was taken to UCLA Medical Center where he was treated, the LA Times said.
Steve Hargrave, Sky's entertainment correspondent, said: "TMZ is a website which goes out of its way to get there first but many of their stories over the years have turned out to be true - particularly with stories from LA.
"You can only imagine the impact of this around the world."
Jackson's manager was not available for comment and officials at UCLA Medical Center could also not be reached.
Sky's US correspondent Greg Milam said: "Clearly he was very seriously ill - we can gather that from what his father and other family members said.
"One member of the family had told the TMZ website that Michael is in "really bad shape" and that the brothers were heading for the hospital.
"His father said he wasn't sure exactly what was wrong and was waiting to hear back.
"One can only imagine what it could be like for his family in such circumstances."
Jackson had been about to embark on a comeback, performing 50 concerts at London's O2 Arena.
The concerts had been due to start the concerts on July 13.
He had been rehearsing in the Los Angeles area for the London shows, which sold out within hours of within hours of going on sale in March.
Hargrave said: "We can't underestimate the effect this will have on Michael Jackson fans who have loved his music and career.
"They would have been assuming that in about three weeks time their idol would have been back on the stage perfoming his greatest hits. To suddenly find out this news will be devastating.
Phil Sutcliffe, from Mojo Magazine said: "He had the extraordinary effrontery to call himself the King of Pop, but that's actually what he was, and for a long, long time."
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