A Chinese mother has been reunited with her infant son after police accepted her explanation that she dropped him into a toilet accidentally immediately after giving birth, a police officer in the eastern province of Zhejiang has said.

The newborn child was rescued by firefighters on Saturday from a sewage pipe under a communal toilet in an apartment block.

"It has been defined as an accident," the police officer at the Punan station in Zhejiang's Pujiang county, told the DPA news agency by telephone when asked about the case on Thursday.

State media said the unidentified 22-year-old woman became pregnant after a one-night stand.

The mother told police she kept her pregnancy secret because she could not afford an abortion and the father refused to help her, reports said.

Firefighters and doctors spent nearly an hour taking the tube apart piece by piece with pliers and saws and finally recovered the newborn, whose placenta was still attached, the report said.

From the time he was found to when he was taken out, the baby was stuck in the tube for at least two hours, it added.

After state television showed footage of doctors cutting the boy from the sewage pipe, many online commentators called for the parents to be punished, while some offered to adopt the boy.