They also rescued a two-month-old baby boy who had a price tag of 50,000 yuan (HK$56,700) and a baby girl who was being sold for 20,000 yuan.

Acting on a tip-off, police raided the underground clinic in a tin-sheeted house on Dalang Street in Baoan district on Tuesday afternoon and arrested 40-year-old doctor Liu Jun.

She originally comes from Henan province and reportedly has a one- year-old child by her Hong Kong boyfriend.

Liu was arrested last March for causing injury to a female patient who had sought an abortion, and was released on bail pending trial.

She reportedly told potential buyers she had helped to deliver the babies.

She claimed the boy was born to a migrant worker whose boyfriend had run away, leaving her alone with the child.

Liu said she paid the woman 20,000 yuan for her baby.

The baby girl was born just 13 days ago to a Jiangxi woman who has two daughters and wanted a son.

Liu assured would-be buyers the babies were healthy and that they would be refunded in full if they were found to be sick. However, buyers would have to pay in advance before taking the babies to a hospital for a medical checkup.

Police raided the clinic as a transaction was in progress.

The babies were taken to the police station and then to a hospital where they are being cared for.

Initial investigations confirmed Liu is not related to the babies.

Police have since located the baby girl's parents in Jiangxi but have yet to trace the boy's mother.

Police said abandoning a baby is illegal but the sentence for trafficking in children is much heavier.

Many Hongkongers own vacation homes in Baoan as properties in the district are relatively cheaper than in downtown Shenzhen.