When Mrs Feng was three months pregnant, officials said they visited her and asked her to fill in an application form and to change her hukou, a Chinese registration permit, to say she lived in the countryside.

It is not clear why Mrs Feng failed to fill in the forms and transfer her residence. She has complained on Weibo, China's version of Twitter, that she was not warned of the consequences until it was too late. But as her pregnancy progressed, local officials offered her family a deal: pay 40,000 yuan ($6250) to smooth the bureaucracy over.

When the couple said they did not have the money, Mrs Feng was taken from her home on May 30 by more than 20 officials and ransomed, her husband said. The officials held her for three days, apparently sending threatening text messages to members of her family, before giving the foetus a lethal injection on June 2.

"[40,000 yuan], it should not be a cent less than that," read one text message, allegedly sent by Yuan Fang, a family planning official, to Mr Deng's sister, Deng Yan. A photograph of the message [pictured] on what appears to be an iPhone has been posted by the family to HSW.cn, a local Shaanxi internet portal by the family.

"I told your father this already and he said he did not have the money, so we did not have a choice. It is you guys that have been careless," the message continued. Mr Deng said he had tried to raise the money until the last minute, but had failed.