Murphy plays an obese woman and her timid husband, plus a third role

Norbit took $33.7m (�17.2m) at the weekend, estimates suggest, well ahead of horror movie Hannibal Rising, a prequel to The Silence of the Lambs.

It was the 14th time that a Murphy film has made its debut on top of the chart.

Diane Keaton's comedy Because I Said So dropped to three, with last week's number one, The Messengers, at four.

Completing the top five was Ben Stiller's comedy Night at the Museum, which remained in fifth place.

Contenders

Three Oscar contenders were further down the box office list, with Pan's Labyrinth at number eight, Dreamgirls at nine and The Queen at 10.

NORTH AMERICAN BOX OFFICE 1. Norbit ($33.7m) 2. Hannibal Rising ($13.4m) 3. Because I Said So ($9m) 4. The Messengers ($7.2m) 5. Night at the Museum ($5.8m) 6. Epic Movie ($4.5m) 7. Smokin' Aces ($3.8m) 8. Pan's Labyrinth ($3.6m) 9. Dreamgirls ($3.1m) 10. The Queen ($2.5m) Source: Media By Numbers

All three were honoured at the Baftas in London on Sunday.

Norbit is based on a story which Murphy developed with his brother Charles, and sees a return to his slapstick comedy roots.

It is not the first time he has played multiple characters and worn a fat suit for a movie - he did so for the Nutty Professor series.

Some US critics have branded Norbit as crass and unfunny, accusing the film of simply playing on racial stereotypes.

But Marvin Levy, a spokesman for producer Dreamworks, said people had to "have a sense of humour" when watching it.