Singer Michael Jackson is believed to have suffered a heart attack at his home in Los Angeles this afternoon.
Reports say that Jackson, 50, went into cardiac arrest and has been rushed to hospital.
He was seen being taken into an ambulance and moved to a nearby hospital, says US gossip website TMZ.
Paramedics were seen performing CPR on the singer, according to the website,
Jackson's mother was said to be at the hospital to meet her son.
It is believed a call to 911 was made from his home in Holmby Hills, LA, at 12.21pm (8.21pm).
A member of the Jackson family told TMZ that 'Michael is in really bad shape'.
An update on the website says, 'We just got off the phone with Joe Jackson, Michael's dad, who says "he is not doing well".'
The singer is due to play 50 sell-out shows at London's O2 Arena starting in July.
But the King of Pop has already had to postpone the first few nights' shows.
Organisers AEG Live said this was in order to make sure everything for the 'massive and technically complex show' was running smoothly.