Sci-fi movie District 9 has gone straight to number one in the US box office.

The debut film from director Neill Blomkamp opened with an estimated $37 million in sales.

The Sony/Tristar film about an extraterrestrial race forced to live in slum-like conditions on Earth knocked Sienna Miller’s G.I. Joe: The Rise of Cobra into second place. Miller’s movie earned $22.5. million last weekend.

The Time Traveller’s Wife, starring Eric Bana and Rachel McAdams, opened in third spot, earning $19.2 million in sales.