Marvel comics adaptation 'Iron Man' kept a steely grip on the top box office slot for a second week as it forges the biggest blockbuster since last year's 'Spider-Man 3', industry figures showed on Sunday.

The fast-paced action film, starring Robert Downey Jr as billionaire industrialist Tony Stark who invents an armoured suit to help him save the world, raked in an estimated $50.5-million Friday through Sunday, Exhibitor Relations said, for a total US-Canada haul of $177.1-million.

It also compiled $170-million in foreign ticket sales, according to the figures, soaring past the likes of comic book heroes Batman, Superman, the X-Men, Daredevil and Catwoman to potentially launch itself as a major franchise for Paramount.

In distant second place with a debut weekend of $20.2-million was 'Speed Racer', a high-tech live-action take on the Japanese boy-drives-car animated series from the 1960s.

Hot on Speed's tail was the brisk romantic comedy 'What Happens in Vegas', in which two people — Ashton Kutcher and Cameron Diaz — seeking comfort in the city of sin wake up married after a night of debauchery. It debuted by earning $20-million.

Slipping two spots to fourth with $7.6-million was another romantic comedy, 'Made of Honor', which stars Patrick Dempsey and Michelle Monaghan as friends who inch towards love as they plan her marriage to another man.

In fifth was former box office topper 'Baby Mama', a surrogate motherhood comedy starring former Saturday Night Live comedians Tina Fey and Amy Poehler, which netted $5.8-million.

'Forgetting Sarah Marshall', billed as "the world's first romantic disaster comedy", was sixth with $3.8-million.

In seventh was 'Harold and Kumar Escape from Guantanamo Bay' with $3.2-million. The sequel to 2004's 'Harry and Kumar go to White Castle' sees stoner buddies landing in the notorious Guantanamo jail after being mistaken for terrorists.

'The Forbidden Kingdom', the first movie pairing of martial arts legends Jackie Chan and Jet Li, dropped from sixth to eighth spot on its third weekend, with $1.9-million.

'Nim's Island', a youth-oriented tropical adventure with Jodie Foster and Abigail Breslin, came in at ninth place with $1.3-million.

Rounding out the top 10 was 'Redbelt', a martial arts action flick penned by renowned playwright and screenwriter David Mamet, which pulled in $1.1-million.

AFP