HONG KONG (AFP) - A Hong Kong movie billed as the world's first 3D porn film has broken the city's first-day box office record previously set by Hollywood blockbuster Avatar.

"3-D Sex and Zen: Extreme Ecstasy" notched up HK$2.8 million ($360,000) on its first day last week, outpacing director James Cameron's science fiction epic which drew HK$2.6 million, the porn movie's publicist told AFP Thursday.

The film has grossed more than HK$15 million since its release, she added.

Curious movie-goers from all walks of life -- office workers, retirees and students -- stood in long queues outside Hong Kong cinemas on the film's first day last week, eager to catch an eyeful of the steamy 3D action.

Loosely based on a piece of classical Chinese erotic literature, the $3.2-million Cantonese-language movie features orgies, swinging and graphic sex scenes.

Set in the Ming dynasty, the film chronicles the story of a young man who, after being introduced to the erotic world of an aristocrat, realises his ex-wife is the love of his life.

The film stars Japanese adult actresses Yukiko Suo and Saori Hara.

The movie, which opened in Taiwan last Friday, and has sparked strong interest in many Asian markets, including Japan and South Korea, as well as Europe and the United States, according to the producer.

In response to popular demand, an extended version of the movie will be released in the coming weeks, producer Stephen Shiu told reporters earlier this week, saying audiences can expect an extra 15 mins of risque scenes.

Travel operators were reportedly organising moviegoing excursions to Hong Kong and Taiwan for tourists from mainland China, where strict censorship rules prevent any screening of the film.

"3-D Sex and Zen: Extreme Ecstasy" opened ahead of reported plans by other filmmakers to produce similar 3D porn movies.

Italian director Tinto Brass has announced he is to produce a 3D remake of his 1979 erotic film Caligula, while Hustler plans to release a pornographic spoof of Avatar, the top-grossing movie of all time.