More than 1,000 furious migrant workers besieged a factory in Shanghai and held 18 Japanese and Chinese managers against their will for more than a day, after the workers were required to abide by unequal regulations. The workers of Japanese electronic appliance maker Shanghai Shinmei Electric staged a strike and besieged the factory for two days, starting around 8am on Friday morning, following the introduction of a new factory policy calling for heavy fines, demerits or immediate termination for workers who made a mistake, the Japan-based Asahi Shimbun reported yesterday. At least one Chinese manager with hypertension passed out after being forcibly detained along with the 17 others - seven Chinese and 10 Japanese - in two office rooms between Friday and Saturday. The company's president, Hideaki Tamura, was among those held. On Saturday night, more than 400 Shanghai police officers freed the managers. Tamura told the Asahi Shimbun by phone that more than 500 workers besieged his office, and the managers were not allowed to use the toilet. Tamura was locked in his office with six other Japanese managers and five Chinese, while the remaining six were locked in another room. The report said the factory's new disciplinary policy was part of a reform scheme after the appliance maker was acquired by a Chinese company last year. Angry workers were cited by the BBC as saying that the new factory regulations, with what they said were 49 unequal clauses, triggered the protest. Another assembly worker, who declined to be named, said they were also angry over the acquisition. She said workers feared that they would no longer enjoy the benefits accumulated in their previous years working in the factory after they signed a new contract following the acquisition by a Chinese firm in Dalian, Liaoning province. She said that several of her colleagues were injured when the anti-riot police rushed into the factory. One worker allegedly suffered broken ribs and another suffered a head injury. Another worker wrote via a microblog about the desperate situation management allegedly put them in. "We earn less than 2,000 yuan [HK$2,468] a month, but we could be subjected to fines of 50 to 100 yuan for arriving late or spending more than two minutes in the toilet," the post said. The company issued a statement yesterday apologising to workers for the new regulations, with a promise that their salaries would be increased.