Chinese police have returned two twin baby girls to their parents after breaking a newborn child trafficking ring.

The girls were allegedly stolen and sold by the obstetrician who delivered them last month in the Fuping district, part of the northern Shaanxi province.

The doctor, Zhang Shuxia, allegedly told the mother that her little girls suffered from "deadly congenital diseases" and convinced her to give them up, China National Radio reported.

Zhang also persuaded her and other relatives not to see the babies after delivery, claiming they had broken arms and legs.

The twins were instead handed to human traffickers who sold them to other families.

Police recovered one girl more than 500 kilometres from her birthplace, in the Shandong province. Her sister was found some 160 kilometres away in neighbouring Shanxi.

The case erupted earlier this week, after parents of another baby delivered by Zhang at the Fuping Maternal and Child Health Care Hospital lodge a complaint with police.

They became suspicious after Zhang talked them into giving their child up, again claiming the baby had a congenital disease and would be a burden.

They were also made to pay a 100 yuan (£10) charge for him to be taken into care.

The baby changed hands four times and was finally sold by traffickers for 60,000 yuan (£6,300) to a farmer in the central Henan province, who had three daughters and desperately wanted a boy.

Police believe Zhang is involved in another 26 similar incidents. Two other suspects have been detained and five health officials have been sacked.

Trafficking of children in China has been fuelled by the country's "one-child" policy and it has been esteemed that human traffickers seize some 200,000 children from their families every year.