BEIJING (Reuters) - Thousands of children in southwest China have been sold into slavery like “cabbages”, to work as labourers in more prosperous areas such as the booming southern province of Guangdong, a newspaper said on Tuesday.

A girl plays at a demolished housing site in Suining, southwestern China's Sichuan province June 11, 2007. REUTERS/Stringer

China announced a nationwide crackdown on slavery and child labor last year after reports that hundreds of poor farmers, children and mentally disabled were forced to work in kilns and mines in Shanxi province and neighboring Henan.

“The bustling child labor market (in Sichuan province) was set up by the local chief foreman and his gang of 18 minor foremen, who each manage 50 to 100 child labourers,” the Southern Metropolis Newspaper said.

“The children generally fall between the ages of 13 and 15, but many look under 10,” it added.

The newspaper said 76 children from the same county, Liangshan, had been missing since the Chinese Lunar Year festival in February, 42 of whom had already left the region to work.

“The youngest kids found in the child labor market were only seven and nine years old,” it said.

According to a contract exposed by an undercover reporter, a child laborer is paid 3.5 yuan ($0.50) an hour and must work at least 300 hours a month.

“These kids are robust and can do the toughest work,” a foreman was quoted as saying, as he pulled a scrawny girl to stand beside him, the paper said.

Xinhua news agency said the county government had sent officials to rescue the children, but some were unwilling to leave, having been sold into slavery by their parents or volunteering to work themselves.

($1=7.002 Yuan)