LOS ANGELES -- "This Is It," a backstage look at the late Michael Jackson's rehearsals for his last concerts, rocked to the top of the North American box office at the weekend, early estimates showed Sunday.

The Jackson film, cashing in on the outpouring of affection for the US pop icon after his death earlier this year, earned $21.3 million in its debut weekend.

The Halloween weekend crowds preferred the last moments of the moon-walking master of the spooky musical hit "Thriller" to scary movie "Paranormal Activity" which took a second spot with $16.5 million.

"Law Abiding Citizen," a thriller about a man bent on avenging the deaths of his slain family, moved up to the number three spot with $7.3 million.

It was trailed by a former number-one "Couples Retreat," starring comic favorites Vince Vaughn and Jason Bateman, now in fourth place with $6.09 million.

The latest in the "Saw" films series, "Saw VI," was in fifth place with $5.6 million, trailed by "Where the Wild Things Are," director Spike Jonze's live-action rendering of the beloved children's book of the same name, with $5.1 million.

In the seventh spot, "The Stepfather, a remake of a 1987 thriller, earned $3.4 million.

"Astro Boy," in eighth place with three million, is a 3-D animated feature film about the futuristic robot who first came to life in the 1950s as a character in the beloved Japanese science fiction manga series of the same name.

"Amelia", a film about aviatrix Amelia Earhart starring Oscar-winner Hilary Swank, reaped $3 million for the number-nine spot.

Teen vampire vehicle, "Cirque du Freak: The Vampire's Assistant," based on a popular young adult book franchise, brought in $2.8 million at number 10.