Advance tickets to shows in several countries sold out within days as fans scrambled to be among the first to see a film billed by Sony Pictures as the movie of "a concert that never happened."

Jackson, who died on 25 June aged 50, spent the previous four months rehearsing in Los Angeles for a gruelling series of 50 concert spectaculars scheduled to begin at London's O2 Arena in July.

More than 800,000 tickets had been sold for the concerts, with organizers promising one of the "most expensive and technically advanced" live shows ever.

Video footage from the rehearsals had been intended to help organizers critique the show and was never intended for public viewing. Sony bought the footage for $60-million after executives saw only several minutes.

The movie also got a stamp of approval from Jackson's long-time friend and confidante, actress Elizabeth Taylor, who was privy to a sneak preview.

Taylor, who recently underwent heart surgery, hailed the movie as the "single most brilliant piece of filmmaking I have ever seen" in a tweet on micro-blogging site Twitter.

"It cements forever Michael's genius in every aspect of creativity."

Despite the anticipation surrounding the film, a group of diehard Jackson fans had launched an online campaign urging devotees of the singer to boycott the movie, claiming it hides the truth about his final days.

The group claims on its website ? "This-Is-Not-It" ? that the movie attempts to mask Jackson's physical frailty as he maintained a punishing schedule of rehearsals.

"In the weeks leading up to Michael Jackson's death, while this footage was being shot, people around him knew that he looked like he might have died," the group said. "Those who stood to make a profit chose to ignore it."

However audience members who saw the first screening on Tuesday said Jackson looked healthy in the film.

"Michael Jackson was very fit. Very healthy. It was the old Michael Jackson, the young Michael Jackson," Hillman said. "I was really surprised how creative and healthy and rhythmic he was."