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Michael Jackson, shown March 5, 2009, was set to play 10 live concerts at the London O2 Arena in July. ((Joel Ryan/Associated Press))

Legendary performer Michael Jackson, whose groundbreaking music and dance moves earned him the nickname the "King of Pop," died in Los Angeles on Thursday after apparently going into cardiac arrest. He was 50.

In a brief news conference, the performer's brother, Jermaine Jackson, said he was pronounced dead in hospital at 2:26 p.m. PT. It's believed Jackson suffered cardiac arrest at his home, but Jermaine Jackson said an autopsy will be conducted to confirm the cause of death.

The autopsy was performed Friday.

Paramedics had responded to a call at Jackson's rented mansion in Holmby Hills about 12:30 p.m. PT, but Jackson was not breathing when they arrived.

Jermaine Jackson said his brother's personal doctor, who was in the house at the time, and paramedics had tried to resuscitate him.

Paramedics continued to perform CPR as Jackson was rushed to UCLA Medical Center, Jermaine Jackson said.

"Upon arriving at the hospital at approximately 1:14 p.m., a team of doctors, including emergency physicians and cardiologists, attempted to resuscitate him for a period of more than one hour, but they were unsuccessful," he said.

"My family request that the media please respect our privacy during this time, and may all love be with you, Michael, always. We love you."

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People wait outside UCLA Medical Center where entertainer Michael Jackson was taken in Los Angeles on Thursday. ((Reed Saxon/Associated Press))

Jackson had been preparing and rehearsing hard for what was to be his greatest comeback. He was scheduled for an unprecedented 50 shows at London's O2 arena, with the first set for July 13.

Frank DiLeo, Jackson's manager, told the Los Angeles Times that at the end of a rehearsal the night before his death, Jackson departed the stage very happy about the progress of the show.

"He just told me how happy he was and that things were finally working out the way he wanted," he said.

Johnny Caswell, a principal at Centerstaging, where Jackson rehearsed for the concerts, told the Times that Jackson was "very frail" but was working hard, putting in six-hour, four-day weeks to prepare.  

In an interview with the L.A. Times last month, Rand Phillips, the chief executive officer of promoter AEG Live, said a medical screening Jackson underwent ahead of the tour revealed "no issues whatsoever."

But family lawyer and spokesman Brian Oxman said Jackson's death was not unexpected. He told CNN that Jackson had been taking medications for past injuries so he could rehearse for his upcoming concerts, set to begin in London in July.

Oxman said his family was receiving reports that his use of those medications was "extensive."

"The people who have been surrounding him have been enabling him," Oxman said. "You think that the case of Anna Nicole Smith was an abuse; it is nothing in comparison to what we have seen taking place in Michael Jackson's life.

"This is something that I feared; this is something that I warned about," he said.

There had been recent reports that Jackson was in poor health and his London concert series, billed as a farewell to London, was postponed by a few days.

However, the concerts quickly sold out, a testament to the enduring appeal of the singer known as the "King of Pop."

Hundreds of fans and media gathered outside the hospital after reports began circulating that he had been transferred there. His family was also reported to be on their way to the hospital.

Jackson left an indelible mark on pop music, largely on account of his 1980s hits such as Beat It and Billie Jean.

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In this Dec. 1, 1984, file photo, pop artist Michael Jackson is shown onstage at opening night of the Victory Tour at Dodger Stadium in Los Angeles. ((Lennox McLendon/Associated Press))

His music set the world dancing, with a catchy beat and innocuous lyrics. His dancing also stunned fans, who watched in awe as he appeared to defy the laws of physics with his backward-gliding moonwalk.

He also set a new standard for music videos with the creative and gripping Thriller, a horror-film spoof that Jackson wrote and produced with John Landis in 1983. He won two Grammy Awards for the Thriller video and MTV named it the best video ever made.

In recent years, he was much in the news for his financial and legal troubles, including the auctioning of personal items and the battle over his Neverland ranch.

His odd personal appearance and relationship with his children also detracted from his image.

But he remained one of pop's most successful musicians, winning 13 Grammy Awards and selling 750 million albums worldwide.

Thriller spent 37 weeks at top of pop charts

Born in Gary, Ind., in 1958, Michael Jackson began his music career at the age of five, joining his brothers Jackie, Tito, Marlon and Jermaine as the lead singer of the family pop music group, the Jackson Five.

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In this 1972 file photo, singer Michael Jackson at age 13, the youngest member of the singing group Jackson Five, sings in his home in Encino, Ca. ((Associated Press))

The group played at nightclubs in the Gary area, and young Michael soon made a name for himself as a singer and dancer of exceptional ability.

In 1968, the Jackson Five signed with Motown Records and moved to California. The group ruled the charts in the late 1960s and early '70s, and its first four singles, I Want You Back, ABC, The Love You Save and I'll Be There, all became No. 1 American hits.  The Jackson Five recorded 14 albums and Michael Jackson recorded four solo albums with Motown.

In 1978, Jackson made his film debut in The Wiz, playing the Scarecrow, with Diana Ross in the lead role of Dorothy.  

Jackson's first big solo success was the 1979 album Off the Wall, which spawned a record-breaking four No. 1 singles in the U.S. and earned Jackson his first American Music Award.  

His 1982 album Thriller made him a musical phenomenon. Produced by Quincy Jones, it spanned a number of pop genres and reigned for 37 weeks on top of the charts.

It produced seven hit singles, and the videos that accompanied them made Jackson's signature moonwalk one of the best-known dance moves in the world. His Bad, Dangerous and HIStory albums also were bestsellers.  

In the 1980s, he racked up industry awards, honours from the United Negro College Fund and the National Association for the Advancement of Colored People, as well as a reputation as one of the world's most beloved entertainers.  

He was a key player in the all-star 1985 benefit single We Are the World, written by Jackson and Lionel Richie, which raised $60 million US for hunger relief in Africa.  

Survived by three children, two ex-wives

But, in recent years, Jackson became better known for his troubled life, and his legal and financial problems, which included battling a variety of lawsuits from former business associates and creditors.  

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This oil on canvas portrait of Michael Jackson dressed as a king, signed by U.S. artist Norman Oak and dated 1995, was one of the singer's possessions sold at auction to cover mounting debts. ((Shaan Kokin/Julien's Auctions/Associated Press))

In 2003, Britain's ITV network broadcast a documentary called Living with Michael Jackson for which British journalist Martin Bashir interviewed the controversial pop star over a period of eight months. ABC purchased the rights to broadcast it to American audiences on 20/20.  

Revelations about Jackson's personal life in the documentary were one of the factors that resulted in his trial on charges of child molestation. He was later acquitted of all charges.  

The months Jackson spent in court took their toll on him. He felt betrayed by Bashir, whom he had grown to trust, and he was forced to watch many former friends testify against him.  

In recent years, there were talks of a comeback tour and another album, but neither materialized.  

Jackson had two brief marriages — to Lisa Marie Presley, whom he married in 1994, and to Deborah Rowe, whom he married in 1996.  

Rowe is the mother of his son, Prince Michael Jackson Jr., and his daughter, Paris Michael Katherine. Jackson's second son, Prince Michael II, was born in 2001, to an anonymous surrogate mother.

With files from The Associated Press