Michael Jackson is dead after suffering a cardiac arrest, sending shockwaves sweeping across the world and tributes pouring in Friday for the tortured music icon revered as the King of Pop.
Jackson, 50, collapsed at his rented mansion in the exclusive Los Angeles neighborhood of Holmby Hills and was rushed to hospital by paramedics before being pronounced dead at 2.26pm (0726 AEST) on Thursday.
One of the most influential figures in pop history whose career included the highest-selling album of all-time, Thriller, Jackson had been preparing for a concert comeback in London next month he had dubbed "the final curtain".
News of his death triggered an outpouring of grief as shocked celebrities, foreign governments and devoted fans from Beijing to Beverly Hills paid tribute to the troubled star.
Lieutenant Fred Corral, a spokesman for the Los Angeles County Coroner's office, said an autopsy would likely be carried out on Friday and would not speculate on the exact cause of death.
Jackson's brother Jermaine, the family's official spokesman, later revealed physicians had battled for more than an hour to revive the star after his arrival at the UCLA Medical Center before he was pronounced dead.
"Our family requests that the media please respect our privacy during this tough time," Jermaine Jackson said. "May Allah be with you, Michael, always."
As the sun began to sink over Los Angeles, a coroner's office helicopter bearing Jackson's body took off from the UCLA Medical Center, where hundreds of media and fans had gathered throughout the day.
Meanwhile police motorcycle riders surrounded Jackson's gated mansion as crowds of tourists and fans congregated.
Pop diva Madonna was among dozens of celebrities who struggled to cope. "I can't stop crying over the sad news," the singer said in a statement. "The world has lost one of the greats, but his music will live on forever!"
The star's first wife Lisa Marie Presley, the daughter of Elvis Presley, said his death had left her speechless.
"I am so very sad and confused with every emotion possible. I am heartbroken for his children, who I know were everything to him, and for his family," Presley told MTV News in a statement.
Political figures also paid their tributes.
California Governor Arnold Schwarzenegger lamented the loss of "one of the most influential and iconic figures in the music industry".
British Foreign Secretary David Miliband also posted his thoughts on micro-blogging site Twitter. "Never has one soared so high and yet dived so low. RIP Michael," Miliband wrote.
But the most visible emotion came in spontaneous gatherings of fans here and across the world.
In Los Angeles Lana Brown, a 49-year-old tourist from Dallas, broke down in tears as she digested the news. "I can't believe we might have lost the best entertainer this world has ever seen," she told AFP.
In New York's Times Square, Chantal de Roy van Zuydewijn watched a giant screen broadcasting the news of Jackson's death with tears running down her cheeks.
"He is a legend. He is a genius," said the 28-year-old Dutch tourist, who had a ticket to the pop legend's scheduled comeback tour in July.
Jackson's death came as the singer prepared to make a keenly anticipated concert comeback in London, his first series of shows in more than a decade.
Jackson family attorney Brian Oxman said he had harboured concerns over the singer's condition, revealing that he had been taking prescription medication as he prepared for his comeback.
Oxman compared Jackson's fate to the overdose death of Playboy centrefold Anna-Nicole Smith, voicing concern over "enablers" in his entourage.
"The people who have surrounded him have been enabling him ... if you think that the case of Anna-Nicole Smith was an abuse, it was nothing to what we have seen in Michael Jackson's life," Oxman told CNN.
While Jackson ruled the charts and dazzled audiences with electric dance moves like the backwards "moonwalk" in the 1980s, his once-stellar career was overshadowed by his colourful public behaviour, his startling physical transformation and multiple allegations of child abuse.
He 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 music superstar, who named his ranch after Peter Pan's "Neverland" of perpetual childhood and furnished it with Disney-inspired rides, struggled to recover.
Born on August 29, 1958, Jackson made his show business debut with four of his elder brothers in the Jackson Five pop group, and went on to lead the stage clan with a piping soprano and dazzling dance moves.
In 1979, Quincy Jones produced Jackson's first solo album for Epic, Off the Wall, a huge disco-oriented success that sold 10 million copies.
They teamed up again in 1982 for what would be Jackson's breakthrough album as a composer and co-producer, "Thriller," which became the top-selling album of all time, with sales exceeding 41 million.
Jones reacted with shock after being informed of Jackson's death Thursday.
"I'm absolutely devastated at this news," he said. "I just don't have the words. Divinity brought our souls together and allowed us to do what we could do through the '80s," Jones said.
Tommy Mottola, the former head of Sony Music who released Jackson's records for 16 years, said the singer had a place in the pantheon of American music icons, alongside Elvis and Frank Sinatra.
"It's one of the greatest losses," Mottola told the Los Angeles Times.
Crowds continued to throng near the UCLA Medical Center and Jackson's home late on Thursday, while street vendors selling hastily designed commemorative T-shirts for $US25 ($A31.09) sought to cash in.
