Thriller Swimfan, about a high school girl stalking the swimming team, has taken the top spot at the US box office.

Despite a largely unknown cast, the tale took $12.4m (�7.9m) in its opening weekend, suggesting teen movies are here to stay.

The low-budget comedy My Big Fat Greek Wedding held on to second place, 21 weeks after it was released, and could soon nudge the $100m mark (�64m).

Oscar-winners Robert de Niro and Francis McDormand teamed up to star in City by the Sea, the third-placed movie this week.

Loosely based on a true story about a police detective who discovers his estranged son is a murder suspect, it took $9.1m (�5.8m) in its opening weekend.

US/Canada Top five

1 Swimfan 2 My Big Fat Greek City by the Sea Signs 5 XXX Source: Exhibitor Relations

Swimfan has been dubbed Fatal Attraction for the high school generation as wayward new student Madison, played by Erika Christensen, tries to come between the talented Ben and his high school sweetheart.

Christensen previously starred as Michael Douglas' drug-addicted daughter in Traffic.

Despite a deluge of films pitched at the teen market in recent years such as Scream, I Know What You Did Last Summer and the Faculty, there seems to be no let-up in their ability to succeed at the box office.

"You cannot under-estimate the teenage audience," said Paul Dergarabedian, president of box-office tracker Exhibitor Relations.

My Big Fat Greek Wedding has been a surprise hit of the summer

Mel Gibson's crop circle thriller Signs is continuing to attract audiences. Six weeks after it topped the box office it remains at number four.

It has become the fourth biggest film of the year, and has become Gibson's most successful film ever, taking $206m (�132m).

But it was a poor weekend overall for the American box office as it grossed the lowest total of the year, with a combined figure of $60.8m (�39m) for the top 12 films.

It is a traditionally slow period for the market and no big movies were released.

Vin Diesel's action thriller XXX rounds off the top five, earning $5.5m over the three-day period.