Blind activist Chen Guangcheng on Thursday accused authorities in his home province in eastern China of seeking revenge for his escape by detaining his nephew and threatening other relatives.

Chen, whose daring flight from house arrest to the US embassy in Beijing sparked a diplomatic crisis, said his nephew Chen Kegui was in police custody in Yinan county in Shandong province after attacking an intruder last month.

Local villagers and Internet reports have said the intruder was a local official angered by Chen's escape.

Chen Kegui went on the run following the incident in late April and was later detained. His wife has been missing for the past few days, Chen said.

"The Shandong authorities are retaliating against me," the self-taught blind lawyer told AFP in a phone interview from a Beijing hospital.

"Yesterday (Wednesday), the public security bureau called us and told the family that Chen Kegui has been formally locked up, and they wanted Chen Kegui's wife to come in and sign a document."

Chen, 40, spent two years under house arrest after serving a four-year jail sentence on charges related to his work exposing forced sterilisations and abortions under China's population control policy.

Since his release from jail in 2010, up to 100 security guards had surrounded Chen's home in Dongshigu village 24 hours a day, preventing him and his wife from leaving their home and preventing outsiders from seeing him.

He is currently in Beijing receiving treatment for injuries sustained during his escape, but has said he does not feel safe in China and wants to leave with his wife and two children to study in the United States.

However, there are fears for his extended family -- including his elderly mother and the parents of Chen Kegui -- who were left behind in Dongshigu.

"Chen Kegui's mother was detained several days ago, after she was detained she was released on bail, right now they are threatening to arrest again," Chen said.

"Chen Kegui's father is confined to the village and cannot leave. They have confiscated his telephone," Chen said.

Phone calls to the Yinan police went unanswered Thursday.

But Liu Weiguo, whose law firm has agreed to represent Chen Kegui, told AFP another lawyer had his licence confiscated by local authorities when he tried to see him in Yinan.

"As lawyers we are seeking to defend Chen Kegui in accordance with the law, but the authorities are refusing to give us access to him, they are violating the law," Liu told AFP.