US top five

1. Spy Kids 2. Someone Like You 3. Heartbreakers 4. Tomcats 5. The Brothers

"It's James Bond for kids. They sort of reinvented a genre and made a huge hit out of it," said Paul Dergarabedian, president of box office monitoring company Exhibitor Relations.

"You've had all these movies that empower women. Now here's a film that empowers kids, and it seems to work."

The film, directed by Robert Rodriguez, also stars Scottish actor Alan Cumming and Cheech Marin, star of cult 1970s movie Cheech and Chong's Up In Smoke.

Executives at the Miramax studio were so confident Spy Kids would be a hit, a sequel has already been commissioned.

The company hopes the follow-up will be released in the summer of 2002, although it could be delayed by possible strikes by Hollywood writers and actors.

Studio estimates also show Ashley Judd's romantic comedy, Someone Like You, made its debut in second place with $10.3m (£7.2m).

Crouching Tiger: Still going strong

Another comedy, Heartbreakers, slipped to third place. The film, starring Jennifer Love Hewitt and Sigourney Weaver, took $8.2m (£5.7m).

Near-to-the-knuckle comedy Tomcats, starring Shannon Elizabeth and Jake O'Connell, made its debut at fourth with $6.5m (£4.5m).

Last weekend's Oscar winners also did well, with Crouching Tiger, Hidden Dragon coming in eighth after taking $5m (£3.5m), pushing its total earnings up to $113.7m (£80m).