Hundreds of enslaved Chinese, among them dozens of children and many suffering from horrific wounds from beatings, are free Friday after police raided thousands of brickworks in central China in a mass rescue operation.

Some 35,000 police officers swept Shanxi province in search of the labourers after local media reported evidence of the atrocities. Residents of Henan province had made an online appeal for help to find dozens of their children who were snatched and sold to human traffickers to work in prison-like kilns across Shanxi. The parents accused the government of official neglect.

It is believed the sudden police action was in response to the local media reports and China's struggle to polish its dismal human-rights image ahead of hosting the 2008 Olympics in Beijing.

Police arrested more than 120 people suspected of owning or running the operations, and have so far rescued 468 slaves after searching 7,500 of the primitive brick kilns across Shanxi and Henan, the Xinhua news agency said. At least 29 of the victims were children and some of the slaves had been in captivity for seven years.

Workers tortured, starved

Despite the massive rescue, the fathers of the missing children who launched the online appeal said it was only the tip of the iceberg.

"Our conservative estimate is that at least 1,000 minors from Henan have been trapped and cheated into back-breaking work in these Shanxi brick kilns," a reporter based in Henan told Chinese state television.

State television broadcast images of the workers, mostly young males with blackened feet, sleeping on bricks inside barred cells. The reports said that children and adult workers alike were routinely starved, tortured and forced to work without payment.

Child beaten to death with a shovel

In one case, a thug accidentally beat a child to death with a shovel and buried the body overnight, state media said.

"We wanted to run but we couldn't," one ragged labourer was quoted as saying. "I tried once and was beaten." Some of the workers shown in the program had festering wounds that appeared to be burns on their feet and around their waist, presumably from working in the kiln, Reuters reported.

Child labour is a widespread problem in China. Recent BBC reports highlighted a factory producing Olympic-branded goods that acknowledged using illegal child labour.