'Thunder' spends third week at US No.1

Action comedy Tropic Thunder has retained the US box office top spot for a third week.

Ben Stiller's latest comedy vehicle holds off competition from Vin Diesel's sci-fi adventure Babylon A.D, which debuts at two.

Elsewhere, Don Cheadle's thriller Traitor enters at five, while Jason Friedberg's spoof Disaster Movie lands at seven.

The top ten in full:

1. (1) Tropic Thunder - $11,500,000
2. (-) Babylon A.D - $9,700,000
3. (4) The Dark Knight - $8,750,000
4. (2) The House Bunny - $8,300,000
5. (-) Traitor - $7,900,000
6. (3) Death Race -$6,228,335
7. (-) Disaster Movie - $6,170,000
8. (8) Mamma Mia! - $4,418,160
9. (6) Pineapple Express - $3,500,000
10. (10) Vicky Cristina Barcelona - $3,003,000