?Police have rescued 151 children and 209 women from crime rings in southwest China's Guizhou Province over the past two years in a campaign against human trafficking, local authorities said Wednesday.

Guizhou police broke up 47 human trafficking rings, detained 81 suspects and punished 450 people since the campaign began in May 2008, provincial police said.

"We will continue to strike hard against human trafficking," said Zhao Xiang, deputy head of the provincial public security bureau.

Human trafficking is a major problem in rural China. Though fewer cases have been reported in recent years, women from poor households are still sold as brides. Moreover, baby boys are abducted so they can be sold to childless couples or couples who want a son rather than a daughter.

The crime gangs typically kidnap women and children in China's poor southwest provinces. They then sell the victims to central and eastern China, reducing the chances the victims can return home.

In addition to the crackdown, Chinese police have stepped up measures to help abducted children be reunited with their biological parents. The measures include a database with DNA samples from children suspected of being kidnapped and their parents.

The database has helped reunite 813 children with their parents, the Ministry of Public Security said in September.