Michael Jackson died after suffering a cardiac arrest, sending shockwaves sweeping across the world and tributes pouring in 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 2:26 pm (2126 GMT Thursday).

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.