The wife of China's jailed dissident Nobel peace laureate is pleading for authorities to ease the conditions of her house arrest, fellow activists said Tuesday, adding her mental state was "very bad".

Liu Xia's husband Liu Xiaobo was jailed in 2009 for 11 years and won the international prize the next year, and she has been under strict surveillance at their flat in Beijing but has not been charged with any offence.

In a brief and rare public statement Liu Xia said she sought three rights: to consult an independent doctor, to access letters she and her husband exchanged, and to earn an income.

The note was posted on the blog of Zeng Jinyan, the wife of another prominent dissident, Hu Jia.

Hu confirmed to AFP that his wife obtained the information but declined to say how for fear of possible consequences.

Liu Xia has suffered increasing depression since 2009 but getting Chinese medical attention could force her to enter a mental hospital, Hu said.

"Liu Xia's mental state is very bad," he told AFP. "Ever since Liu Xiaobo was jailed she suffered slight depression, and after Liu Xiaobo won the prize and she lost her freedom, her depression became more severe.

"She can't accept treatment from a Chinese doctor, because if she is diagnosed as having serious depression, then she might be thrown into a psychiatric hospital for mental illness."

Zeng in her blog added that Liu Xia faced increasing financial straits -- in particular after her brother Liu Hui was sentenced this year to 11 years' jail for fraud, in a case that relatives suspect was political retaliation.

"Liu Hui's imprisonment has not just cut off a source of income, the legal costs have also deprived the family of a large amount of funds and brought economic hardship," Zeng wrote.

Liu Xiaobo was jailed for subversion after spearheading Charter 08, a bold petition urging greater protection of human rights in China.

His Nobel award in 2010 incensed Beijing, which deals harshly with dissidents and other potential threats to its authority.

In mid-November Liu Xiaobo's lawyer announced he would appeal the dissident's conviction at the request of Liu Xia.

In June this year Liu Xia addressed an appeal to President Xi Jinping, saying: "What we should see from national authorities is justice, not merciless oppression".