By Julian Marshall
Newsbeat online editor
Madonna has described Michael Jackson as one of the "greatest" ever artists at a concert in London.
The singer was performing at the O2 Arena on Saturday, where Jackson was due to begin a residency this month.
During her hit single Holiday, a dancer, dressed as Jackson in a single glove, hat and white socks, performed a dance routine to Billie Jean.
Madonna said: "Let's give it up for one of the greatest artists the world has ever known."
Above the stage an image of Jackson as a child was shown.
Later in the show, further recognition was given to to Michael Jackson when the lyrics to his single Man In The Mirror were shown on the big screen behind the stage.
Jackson, who died last week aged 50, will be officially remembered at a public memorial service on Tuesday.
More than a million fans have already applied for 17,500 free tickets for the event in Los Angeles.
Tickets will be allocated on a random basis.