District 9, a gritty, low-budget space alien movie set in South Africa with a cast of unknowns, opened as Hollywood's No. 1 film, grossing more at the box office its first weekend than it cost to make.

The sci-fi action thriller depicting extraterrestrials as unwanted immigrants stranded in Johannesburg took in $37 million in North America, distributor Sony Pictures said on Sunday.

It said District 9 cost less than $30 million to make, a modest budget by Hollywood standards.

The film was buoyed by rave reviews and a promotional blitz at the recent Comic-Con comic book convention, which fueled strong pre-release interest among sci-fi fans.

The studio also touted the fact the movie, shot in a faux documentary style, was produced by Peter Jackson, the filmmaker behind the blockbuster, Oscar-winning The Lord of the Rings trilogy.

The new film was directed and co-written by South African native Neill Blomkamp, a protege of Jackson who is making his feature directorial debut after a career of doing commercials.

The cast stars South African newcomer Sharlto Copley as a bureaucrat leading the forced eviction of alien creatures from a Johannesburg slum, District 9, where they have been settled since their ship stalled over the city 20 years earlier, marooning them on Earth.

The confrontation escalates quickly into a bloody struggle by the humans to gain control over the sophisticated weaponry of the crustacean-like extraterrestrials. The story was adapted from a short film, Alive in Joburg, that Copley had produced with Blomkamp as director.

Rory Bruer, president of worldwide distribution for Sony Pictures Entertainment, said the story line and setting of the film obviously caught on with the mostly male, young moviegoers who made up its initial core audience.

It's so out-of-the-box different from most movies that you see from a major studio, Bruer said. It's kind of a rogue, raw, visceral film that has a life of its own.

STRING OF LOW-BUDGET HITS

District 9 is Sony's third film in the below-$40-million budget range to find success in recent weeks, following the culinary-themed Julie and Julia, which grossed $44 million after two weeks in release, and the romantic comedy The Ugly Truth, with a $77.5 million tally from four weeks of business.

With a debut of $37 million, 'District 9' proves that you don't have to spend $200 million to make a great sci-fi film, said Paul Dergarabedian, analyst for Hollywood.com Box-Office.

Last week's No. 1 film in the United States and Canada, Paramount Pictures' G.I. Joe: The Rise of Cobra, fell to No. 2 this weekend with a Friday-through-Sunday estimated gross of $22.5 million.

That's down nearly 60 percent from its opening weekend, leaving the film inspired by the G.I. Joe line of toy soldiers with a total of nearly $100 million so far.

Another film debuting in wide release this weekend, Warner Bros' romantic fantasy The Time Traveler's Wife, based on a best-selling novel, grossed $19.2 million to open at No. 3. Julie and Julia slipped a notch to No. 4 with $12.4 million.

Disney's guinea pig adventure G-Force rounded out the top five this weekend with $6.9 million in ticket sales, bringing its tally to $99 million. Ponyo, Disney's English-dubbed version of a film from Japanese animator Hayao Miyazaki, opened at No. 9 with $3.5 million.

The only other new wide release in the top 10 this week was the Jeremy Piven comedy The Goods: Live Hard, Sell Hard, from Paramount Vantage, which grossed $5.4 million to open at No. 6.

Warner Bros' Harry Potter and the Half-Blood Prince rang up another $5.2 million this weekend, ranking No. 7, as its domestic cumulative total climbed to $294 million.

South Africa