Local authorities in southern China have admitted they took a baby boy from his parents 32 years ago based on the country's one-child policy, sending a shockwave.

Government-affiliated online media and other outlets are reporting that a one-year-old boy was taken from a couple in the municipality of Quanzhou in the Guangxi Zhuang Autonomous Region in 1990.

The couple last month filed a petition with police seeking an investigation into the whereabouts of their seventh child.

Local health authorities responded in writing last Friday that children who were born in violation of the population control policy at the time were subject to what they called "social adjustment" based on decisions by local governments.

The one-child policy triggered illegal abortions, child trafficking and other issues in China.

It is unusual for local Chinese authorities to admit that they were involved in taking children from their parents based on that policy.

The whereabouts of the boy remains unknown.

On Chinese social media, a barrage of criticism is directed against authorities. One person says if an ordinary person takes away a child from the parents, it would be called kidnapping, but it will be social adjustment if authorities were involved.