Michael Jackson was reported to have died tonight after suffering a heart attack at his Los Angeles home.

The Los Angeles Times reported that Jackson was not breathing when medics arrived at his home, and they performed cardiopulmonary resuscitation. He was then rushed to the UCLA Medical Centre hospital. The TMZ website later reported that he had died.

Jackson, 50, was due to start a series of comeback concerts in London on July 13 running until March 2010. The singer had been rehearsing in the Los Angeles area for the past two months.

The shows for the 50 London concerts sold out within hours of going on sale in March, and these will now be thrown seriously into doubt.

There have been concerns about Jackson’s health in recent years but the promoters of the London shows, AEG Live, said in March that Jackson had passed a four-and-a-half hour physical examination with independent doctors.

Jackson was pronounced dead after arriving at the UCLA Medical Center, having been found unconcious on Thursday afternoon at his home in the neighbourhood of Holmby Hills, Los Angeles coroner Fred Worral said.

Paramedics had earlier been sent to Jackson's home in the Bel-Air area of the city but were unable to revive him, the Los Angeles Times reported.

Hundreds of people massed outside the hospital after news of his arrival there emerged.

Many of them burst into tears as his death was announced.

Jermaine Jackson, the singer's brother, said: "This is hard. My brother, the legendary King of Pop, Michael Jackson, passed away ... It is believed he suffered cardiac arrest in his home."

"Our family requested that the media please respect our privacy during this tough time. And we all will be with you Michael, always. Love you."