The crackdown came after 10 children aged between three and four years old were kidnapped in the city, which is home to a large population of migrant workers, since the beginning of the year, a police statement said. The tenth child has not yet been accounted for.

The gang sold the children to couples desperate for a child for between 1,000 yuan and 8,000 yuan (US$120 and US$960) each, the English-language China Daily newspaper reported.

The children were abducted from families of migrant workers in Shenzhen, an economically developed city in Guangdong province just across the border from Hong Kong, and sold to farm families elsewhere in the province, the newspaper quoted Li Feng, director of public security in Shenzhen, as saying.

"Shenzhen police never considered the issue of child abduction as a priority, therefore they had not seriously tried to solve the problem," former Shenzhen police officer Gao Peiqi told RFA's Mandarin service. "However, in recent years, as more and more families became victims of child abduction, parents’ voices have become louder and louder in demanding the society and police for help."

Of the nine rescued children, six were identified using DNA tests and returned to their parents Wednesday. The prime suspect, identified only by a family name Xu, is 47 years old and from Guangdong, the report said. Xu reportedly asked his 10-year-old son to lure a three-year-old boy with candy.

Hu Xingdou, a Beijing professor who has studied China’s societal problems, believes child abduction is partially caused by children not going to school. “Many migrant workers in big cities cannot afford to send their children to school due to high fees.”

“In some remote rural areas, due to the imbalance of the male and female population as well as poverty, many men are not able to find wives and hence they have no children. Others want boys instead of girls. This causes child abduction to become a wide spread phenomenon, which in many places is not even considered a criminal act. [The kidnappers] actually think they are doing something good for those who want children,” he said.

Most of their parents are transient workers, who hold busy jobs selling merchandise on the streets and often leave their children unattended. They can also be less wary than city folk, especially if they hail from a rural background where strangers are easily noticed.