A 16-year-old girl, kept prisoner in her own home for 15 years by her mentally ill mother, has been rescued by authorities in Harbin, capital of northeast China's Heilongjiang Province, a local newspaper reported on Saturday.

Police broke into their apartment on Tuesday and took Jiang Wei, 16, and her mentally disturbed mother, Jiang Binlan, 56, to hospital, China Daily reported.

A neighbour in Jiang Binlan's apartment block, Chen Gui, raised the alarm. Chen had the vague impression that a woman and her daughter lived in the building where he has lived for the past 15 years, but he had never seen them.

A month ago, Chen found on his doorstep a neatly folded letter written by the girl. It was a cry for help and Chen went to the local authorities.

The unbelievable story evoked widespread concern from the public after it appeared on a local newspaper this month and was soon followed by many other media organisations.

The mother had severe schizophrenia and tuberculosis and had been forced to retire early from her job at a construction company. A sudden divorce from her husband also contributed to the belief that someone might try to take her daughter away from her, the report quoted the girl's uncle as saying.

Many neighbours in the community are providing food and clothes for the mother and daughter and have promised to support the girl in the future.