BEIJING (AFP) - A man in central China kidnapped five children from a park over the weekend, led them to a storage room and stabbed four of them to death, a local official and rights group said Monday. It was the latest in a series of violent assaults on children in China - often involving people with suspected psychiatric problems - which experts have blamed on rapid social change as the country's economy booms. According to the Hong Kong-based Information Center for Human Rights and Democracy, a 22-year-old man grabbed the children from a park in Henan province's Shenqiu county and took them to a nearby storage room. An official at the government of Huaidian, a small town in Shenqiu where the crime took place, told AFP the suspect killed four of the children and seriously wounded another on Saturday evening. The centre said the victims were all stabbed, adding they were around 10 years old. The suspect has already been detained by police. "The suspect is a young man from Anhui (east China) and he lives with his mother in Shenqiu," said the official, who refused to be named. He would not provide further details. A spokesman for the county government, surnamed Yang, said the suspect was unemployed. "As for why he did it, I can't say anything as police are investigating," he said, refusing to comment further. The centre said the suspect was a former policeman from the area who had been sacked and wanted to exact "revenge on society", but both officials denied this. China has been hit by several violent attacks against children over the past two years that have forced authorities to increase security around schools and brought calls for more probes into the root causes of such acts. In September, a farmer with mental health problems killed six people, two of them children, with an axe as they made their way to a kindergarten in Henan. A month before that, eight pupils were hurt when a staff member at a day care centre for migrant workers' children in Shanghai went on a stabbing spree. Last year, at least five major attacks took place at schools in China, killing 17 people - including 15 children - and wounding more than 80.