Jackson is widely credited with revolutionising pop music with albums including Bad and Thriller, but his career was tainted with allegations of child abuse.

He was due to perform a highly-anticipated 50-date "farewell" residency at the O2 Arena in Greenwich, south London, starting next month. Fears for his health emerged after he postponed the first dates.

Jackson lived as a virtual recluse following his 2005 acquittal on charges including child molestation and plotting to kidnap his young accuser. Despite his acquittal, the trial was a body blow from which the pop superstar struggled to recover.

Four years later, Jackson is still worshipped by fans and lauded by critics, for his infectious, dance pop music. The attention, however, paid to him in recent years has been less flattering, focusing on repeated cosmetic surgery - which he always denied - his baby-dangling antics and a decade of child abuse claims.

His friend, the performer Uri Geller, said last night there had been no indication that the singer was in such a frail condition.

"I'm absolutely devastated and shocked. I really have no words," he said. "He was a young and terribly fit man and he was getting ready for performances in England. He was just fine, the last I heard."

Matt Blank from the Michael Jackson World Network fan club said he was "a bit dumfounded and a bit shellshocked by it all".

He added: "I find it hard to believe this could be a reality.

"In the past, health issues of Michael Jackson have always been rumoured. I can only imagine this is down to the amount of stress he was under to come out and perform."

He added: "It's just unimaginable that Michael Jackson is no more, it's just unbelievable."

Brian Oxman, a Jackson family lawyer, told CNN he was told by the star's brother, Randy Jackson, that he had collapsed at his home in west Los Angeles.

A cardiologist at UCLA told showbiz website TMZ.com that Jackson died of cardiac arrest after failing to respond to attempts at resuscitation. It also said his sister LaToya ran into the hospital sobbing.

A spokesman for the hospital declined to comment.

Jackson last toured 12 years ago when he played 82 shows in 58 cities for the History tour. He has spent time living outside the United States since his 2005 acquittal on child molestation charges.

AEG Live, which organised the O2 concerts, said Jackson had passed a lengthy physical exam in early 2009, before the London concerts were announced.

Born in 1958, Jackson made his musical debut with four of his older brothers in the Jackson Five before launching his solo career. As his life was complicated by his meteoric rise to fame, he also started undergoing a dramatic physical transformation.

In 1994, he married Lisa Marie Presley, the 26-year-old daughter of Elvis Presley. The couple separated two years later and Jackson later remarried Debbie Rowe, a 37-year-old nurse he met while undergoing plastic surgery in 1997. They had two children, Prince Michael and Paris Michael Katherine, before divorcing in 1999.

Jackson had custody of the two children and of a third, Prince Michael II, whose mother's name has never been made public. Press from Telegraph http://www.telegraph.co.uk/culture/music/michael-jackson/5642715/Michael-Jackson-dies-aged-50.html