Thirteen members of a Chinese criminal gang that trafficked abandoned or stolen babies have been arrested, police say.

Seven infants were rescued during the operation in the central city of Wuhan about a week ago.

The gang's activities came to light when railway police arrested two women transporting babies from south-western Yunnan province.

The women claimed the babies were their own, but DNA tests showed otherwise.

Over the next few days, police managed to rescue five more babies at the same railway station, and arrest those carrying them.

Boys fetch more

Further arrests were made in Yunnan province.

Gang-members have admitted abducting and selling at least 22 babies, but police think the real number may be much higher.

The one-child policy leaves many families without a male heir

According to the China Daily, the babies - unusually mostly girls - had all been abandoned, stolen or sold in rural areas of Yunnan.

They were being taken to central Henan province to be sold, probably to farmers.

The gang sold baby girls for the equivalent of about $180, while boys fetched much more - about $2,400.

In rural areas, there is a high demand for boy babies because of China's one-child policy, which leaves many families without a male heir.

However girls are also bought by farming families as future servants or wives for their own sons.

According to a UN report last year, more than 250,000 women and children have been the victims of trafficking in China in recent decades.

Selling children was outlawed by the Communist Party when it came to power in 1949, however correspondents say it reappeared in recent years amid loosening social controls.