The wife of a recently detained human rights activist issued an open letter to President Xi Jinping calling for the release of her husband and the implementation of the constitution.
Zhang Qing, wife of legal reform advocate Yang Maodong, said she had been stricken by despair since learning of her husband's detention on August 8 and wanted to lodge a strong protest.
Yang, better known by his pen name Guo Feixiong, was detained on a charge of "assembling a crowd to disrupt order in a public place", the US-based Chinese Human Rights Defenders said.
"I want to tell you and tell the world about the brutal suffering of a prisoner of conscience Guo Feixiong over the past 10 years," wrote Zhang, who is living in Texas with her daughter.
Zhang said she once had a "sliver of hope" that human rights and the rule of law would be respected in China when Xi expressed his commitment to "firmly establishing the constitution" shortly after being installed as Communist Party chief in November. The remarks were seen by advocates of political reform as evidence that Xi might be willing to consider making the party subservient to the law.
"But we have now been dealt a severe blow, and we are in despair," said Zhang, who said that her daughter was also shocked by Yang's detention.
"Mr Xi Jinping, you also have a daughter. Could you please tell me how I should talk to and comfort my daughter in such an environment?" she asked.
Zhang had previously written eight open letters to Chinese leaders, but received no reply, as she had expected.
"I will not give up working hard, no matter whether or not I get a response," she said.
Yang was sentenced to five years in prison in 2007 after writing about political corruption. He was released in September 2011.
Zhang told the South China Morning Post that authorities have not replied to a request by Yang's lawyer for a meeting with him.
"We want to have a meeting with him as soon as possible to find out on what grounds and circumstances he is detained, and find out how is he now," she said. "It is a difficult time for me now."
Rights groups have reported a crackdown on political activists since Xi was formally appointed president in March, saying at least 24 activists had been detained.
The activists include lawyer Xu Zhiyong , who called for the release of activists who were arrested for demanding that government officials disclose their assets.