Irate middle school students in Shenqiu county, Henan province , laid siege to the county government office building yesterday after their playground was torn up by a local property development company early that morning, according to the Information Centre for Human Rights and Democracy. The incident ended last night after local authorities promised to negotiate with the developer to rebuild the playground. Yesterday morning at least 4,000 students gathered at the playground hand in hand to try to prevent the developer from destroying the site, a statement from the centre said. Two female students were injured by policemen during the clash. The developer had planned to refurbish the grounds into what the centre described as a high-class 'European garden' project. After noon, more and more angry students gathered at the county government offices, breaking the door and the windows of the building and even starting a fire to express their anger, the centre said. Hundreds of armed policemen were sent to control the crowd, and dozens of students were injured in the conflict. The students stayed in front of the building until 8pm, when the promise from authorities sent them home. However, police cars continued patrolling the neighbourhood around the government building throughout the night. Netizens uploaded a video of the clash on popular mainland forums including Tianya.cn. In June, about 30,000 mainland students and residents set police cars and government buildings on fire in Wengan , Guizhou province , after a 17-year-old girl was raped and murdered. The protest, with more than 150 government offices damaged and 40 police vehicles torched, was against the police handling of the murder investigation. Later, however, state media reported there were deep-rooted grievances behind the protest, including demolition of homes and relocation of residents.