A maintenance worker surprised passers-by near a Chinese railway station when he starting watching a banned porn film, not realising his computer was connected to a giant screen, state media said Tuesday.

The worker, identified only by his surname Yuan, was supposed to repair the screen, on a building near the main railway station in Jilin in northeast China, the Global Times reported.

But when he began playing "The Forbidden Legend: Sex and Chopsticks", hundreds of local residents stopped to watch as well, the official Xinhua news agency reported.

The company which owns the screen called him after about 10 minutes, and he immediately disconnected the computer before throwing the disc out of a window, the Global Times said.

The film is based on a classic Chinese erotic novel, "The Plum in the Golden Vase", set in the Northern Song dynasty in the early 12th century and centred on Ximen Qing, a corrupt social climber and womaniser who has six wives and concubines among his 19 sexual partners.

The story follows the women's domestic sexual struggles as they seek prestige and influence. Although identified as pornographic and officially banned for centuries, the work -- by an unknown author -- has been read by many educated Chinese and was first translated into English in 1939.

The Hong Kong-made film has a similar plot but is much more explicit, and is banned on the mainland.

Police were investigating the incident, Xinhua said.

According to Chinese law, individuals who spread pornographic audiovisual products can be sentenced to up to two years in prison.