More than 1,000 people protesting about a power blackout blocked traffic in a Shanghai neighbourhood, residents and local media said yesterday. It was one of three blackout protests in the city on Monday night, highlighting government worries that electricity shortages could affect social stability as well as Shanghai's businesses. Officials have repeatedly stressed that measures to save power, such as forcing companies to shift working hours, would not affect residential users. However, record demand has stretched Shanghai's power grid to the limit, causing blackouts in some areas. At the Tianchi residential complex in the eastern Pudong district, more than 1,000 households lost power on Monday. Unable to sleep in the heat, many went outside, and the gathering later grew into a protest. Witnesses said several police arrived at the scene as the crowd grew. The householders became increasingly agitated during the five hours it took to fix the power cut. Local police declined to say if arrests were made, but the Shanghai Daily newspaper said no injuries or vandalism were reported. 'It became very noisy as many people went out into the street. Community officials arrived soon and tried to comfort unhappy people. More than 10 policemen came later to maintain order,' a resident said. Public protests are rare in Shanghai and any demonstrations are closely monitored by police. Two other areas, in the northern Zhabei district and western Xuhui district, reported similar incidents on Monday night, while people blocked a street in Pudong's Zhuyuan residential complex on Sunday during a protest over a blackout that lasted nearly three hours. 'I saw the street was blocked by people. Some neighbours complained that the repair workers were too slow,' said Zhuyuan resident Grace Zheng. Shanghai's heatwave, which saw temperatures top 36 degrees Celsius for seven days in a row - hitting 39 degrees at one point - broke yesterday with heavy rain. The American Chamber of Commerce in Shanghai met officials last month to discuss the power shortage, which is making the city less attractive as a business destination. 'For the past two years, electricity shortages have affected industrial enterprises in east China, with many manufacturers forced to alter their production schedule,' the chamber said.