A trio of Spy movies dominate the US box office as XXX enters the chart at number one.

Vin Diesel's action thriller XXX took $46m (�30.1m) in its opening weekend, according to studio estimates.

It knocked Sixth Sense director M Night Shyamalan's latest offering, Signs, starring Mel Gibson, into the second spot.

The movie about crop circles has taken a total of $118 (�77.3m) since its release two weeks ago.

Crime caper Spy Kids 2: The Island of Lost Dreams entered at number three, taking $17m (�11.1m) in its first three days.

Top five

1. XXX 2. Signs 3. Spy Kids 2 4. Austin Powers: Goldmember 5. Blood Work

And comic super sleuth Austin Powers' Goldmember fell two places to number four, with a tally of $13m (�8.5m) in its third week of release.

In XXX Diesel plays an underground adrenalin seeker forced by the authorities to infiltrate a Russian crime ring or face going to jail.

Joaquin Phoenix and Mel Gibson star in Signs

The movie reunites Diesel with director Rob Cohen, who directed the star in the surprise hit of 2001, The Fast and the Furious.

In just a short period, Diesel has proved himself as an action star who can lead a movie and bring in the all-important audiences in their 20s.

A new entry at number five is Blood Work, Clint Eastwood's crime thriller, in which he plays a retired FBI director who goes back on the trail of a serial killer after undergoing a heart transplant.

After a record-breaking start to the summer box office figures have been tailing off in recent weeks.

"This is the fourth down weekend in a row," said Paul Dergarabedian of box office tracker Exhibitor Relations.

"We're still on track to surpass last year's summer box office, but it's going to be tighter than we thought."