It is a vision of hell on earth: green hills blasted into black heaps, and workers toiling under snarling machinery, dodging hot red sparks and rivers of molten metal.

Inspired by Dante's "Inferno", a medieval tale of a journey to the underworld, Zhao Liang's latest documentary presents a bleak vision of China's breakneck industrialisation.

"Behemoth" won rave reviews at international film festivals. But the director says a ban by Communist officials mean only a handful of people in his home country will see it.

A screening in Beijing this month was a far cry from Venice Film festival's red carpet, where Zhao waved for photographers in September.

Instead a small audience, largely fellow filmmakers and artists, watched his chronicle of the ripping apart of China's Inner Mongolia region in the pursuit of economic growth.

Zhao said afterwards that the film's setting "offered the kind of visual spectacle I was looking for. The environment was just too shocking."

The area is dominated by pitch black -- open-cast mines gouged into hillsides and coal dust ingrained in miners' faces -- and blood red: plumes of flame and pools of liquid metal at a steel plant.

Quotes from the 14th-century Italian poet are read over hellish images: a crawling snake and coal trucks stretching serpent-like to the horizon.

After rapturous applause, an audience member asked whether the film would be screened more widely.

Zhao, 45, looked downcast, responding: "I know that it's not possible. The Inner Mongolian government gave an order that the film could not be promoted."

LIVES SACRIFICED

The director is part of a generation of independent documentary-makers in China who shunned the country's state-dominated production system to shoot unflinching and gritty social portraits.

His "Crime and Punishment" was an indictment of a dysfunctional legal system, as reflected by a shambolic police station in a small town on the border with North Korea.

In "Petition", he followed peasants battling bureaucracy over a 12-year period, and "Together" documented the shortcomings of China's care for people with HIV/AIDS.

The Beijing screening -- one of just three so far in China -- was held at a film school run by art critic Li Xianting, sometimes known as the godfather of the country's independent cinema.

White-bearded Li, who has a monkish air, noted the similarities between Zhao's films and the critiques of industrialisation made by European artists in the 19th century.

"This film is a reflection of crazed urbanisation, GDP growth... whose cost (is) in the lives of so many on the bottom of society," he told the audience.

"China has all this money. Where did it come from? From the sacrifices of all these lives."

Li funds filmmakers and for years hosted an annual independent documentary festival, but under the leadership of President Xi Jinping China has tightened already strict regulations on culture.

Police cancelled the event in 2014, when thugs were hired to intimidate festivalgoers, and called it off again last year, Li says.

"From a screening perspective, the restrictions are becoming ever greater," Zhao told AFP in his artist's studio.

'EXPOSING LIES'

Independent documentaries can only circulate in the country through pirated DVDs and private screenings.

One enthusiast shows films weekly in a Beijing nightclub -- literally underground. A movie screened there this month was based on interviews with a victim of Mao Zedong's political campaigns in the 1950s and 60s.

Zhao said independent films offered one of the few honest lenses on Chinese society, where the ruling Communist party imposes strict censorship.

"Most media in China are engaged in covering up the facts, in lying. Many documentaries are about exposing lies, and letting people see the truth."

Zhao relied on French and Italian funding and took nearly two years to make "Behemoth", a process he called "guerilla filmmaking" involving regular run-ins with authorities.

The human costs of natural resource extraction is shown through the plight of miners who have developed black lung disease through years of exposure to coal dust.

Middle aged sufferers are filmed in tight close-ups, having their lungs washed out with rusty hospital equipment and lying hopelessly on their beds struggling for breath.

As many as six million people are estimated to suffer from the incurable illness in China.

"Black lung disease is something I've paid attention to for a long time," Zhao said, adding wistfully: "Ideally, the film would be able to be screened in China, for Chinese people."