Adventure film National Treasure: Book of Secrets has topped the US box office for the third week in a row.

The thriller, which stars Nicolas Cage, has seen off stiff competition from Will Smith's I Am Legend to stay at number one for another week.

Book of Secrets, a sequel to the original National Treasure, sees Cage battle the authorities as he seeks to clear his family's name and uncover a historical secret.

The film earned an estimated $20.2 million (£10.25 million) this week to take its total takings to $171 million (£86.77 million).

Meanwhile, Will Smith's I Am Legend is also doing well at US cinemas as it sold $16.4 million (£8.32 million) in tickets in the fourth week since its release. The post-apocalypse horror film which sees Smith try to find a cure for a killer disease, has earned over $225 million (£114 million) so far and is shaping up to be a massive hit.

Comedy films also had a good week at the box office with Warner Brothers comedy Juno raking in $16.2 million (£8.22 million) to come in third this week. Children's film Alvin and the Chipmunks also experienced a good week at the cinemas with an estimated $16 million (£8 million) in ticket sales taking its total earnings to $176.7 million (£89.6 million).

07/01/2008 07:33:03