The Devil Inside tops US box office

Image caption, Paramount bought the film, co-written and directed by William Brent Bell, for $1m

Low budget horror film The Devil Inside has spirited its way to the top of the North American box office, taking $34.5m (拢22.4m) on its opening weekend.

It is the tale of a woman investigating exorcisms performed on her mother.

Like Paranormal Activity and Cloverfield before it, the film is released by studio Paramount and is filmed in a mock-documentary style.

Last week's number one, Mission: Impossible - Ghost Protocol, dropped to two, with receipts of $20.5m (拢13.3m).

As with 2007's Paranormal Activity, which has gone on to spawn two sequels, and 2008's Cloverfield, which topped the US and Canada box office in January 2008, The Devil Inside benefited from a cryptic online marketing push.

Don Harris, president of domestic distribution for Paramount, said: "The marketing campaign was very much like Paranormal [Activity].

"It was online, trying to find the younger movie-goer, the fans for this genre."

Paramount bought the independently-produced film - which has been widely slated by critics - for just $1m (拢648,000).

The success of the film, the only new release in the US last week, took many industry experts by surprise.

"This one caught everyone looking, but the devil got his due," said Hollywood.com analyst Paul Dergarabedian said.

"It's just very difficult to track the horror fan base, no question about it."

Sherlock Holmes: A Game of Shadows dropped a place to number three, taking $14.1m (拢9.1m).

Guy Ritchie's film, starring Robert Downey Jr and Jude Law, has now taken $157.4m (拢102m) in North America since its release on 16 November.

David Fincher's film adaptation of Stieg Larsson's The Girl with the Dragon Tattoo climbed a place to number four, with $11.3m (拢7.3m).

And family film Alvin and the Chipmunks: Chipwrecked dropped two to five, taking $9.5m (拢6.2m).