The latest film adaptation of CS Lewis' Narnia books has taken the top spot at the US and Canadian box office - knocking blockbuster Iron Man into second place according to studio estimates.

'The Chronicles Of Narnia: Prince Caspian' sold $19.3 million(10million) worth of tickets during its first day of release across the United States and Canada on Friday, distributor Walt Disney Co said on Saturday.

Marvel Entertainment Inc's superhero smash 'Iron Man' the box office champ for the past two weekends, was the No. 2 choice on Friday, with estimated sales of $8.6 million (4.5million), according to tracking firm Box Office Mojo.

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Growth spurt: Skandar Keynes (Edmund Pevensie), Georgie Henley (Lucy Pevensie), William Moseley (Peter Pevensie), Anna Popplewell (Susan Pevensie) on the red carpet at the premiere of The Chronicles of Narnia: Prince Caspian in New York

Industry observers had expected 'Prince Caspian' to do better than the first 'Narnia' film, 'The Lion, The Witch And The Wardrobe' But that film earned $23 (11.5 million) on its first day in December 2005, and $65.6 million in its first weekend.

By contrast, observers were looking for the sequel to earn in the $80 million(40million) range this weekend. Estimates for the three-day period will be issued on Sunday.

A Disney spokeswoman declined to make an early forecast for the weekend. Family-friendly movies, such as the 'Narnia' films, usually count on strong turnouts on Saturday and Sunday.

The lucrative summer moviegoing season is off to a wobbly start. Last weekend, the kids movie 'Speed Racer' crashed to a dismal $18.6 million during its first three days. On the other hand, 'Iron Man' has surpassed all expectations, and has grossed about $200 million to date.

The 'Narnia' series, based on the religious-themed books by C.S. Lewis, are co-produced by Walden Media, a film company owned by Denver billionaire Philip Anschutz. Both films were directed by New Zealander Andrew Adamson, a veteran of the 'Shrek' series.

Critics were less enthused by the new 'Narnia' film, with 66 percent of top reviewers giving their approval, according to Rotten Tomatoes (http://www.rottentomatoes.com), a Web site that collates reviews. The first film garnered a 78 percent rating.

Work is under way on a third film, 'The Voyage Of The Dawn Treader' with British documentary veteran Michael Apted stepping in for Adamson, who will serve as a producer.

The Chronicles of Narnia: Prince Caspian is released in cinemas across the country on June 26th.