Friends of Chinese artist Liu Xia say her health has deteriorated and she is in urgent need of medical care to treat a heart condition.
The 53-year-old Liu is married to jailed Nobel Peace Prize winner Liu Xiaobo. She has been held without charge under house arrest for three years because of her husband's activism.
Lawyer and family friend Mo Shaoping says Liu was recently rushed, along with a large police escort, to a Beijing hospital with heart problems. Mo says the hospital inexplicably asked her to leave after just one day, even though she needed additional care.
She has also complained of depression because of her extended solitary confinement, but has been hesitant to seek medical treatment out of fear the government may send her to a psychiatric hospital.
The poet, painter and photographer is only occasionally allowed to see her husband who is serving an 11-year prison term after being found guilty in 2009 for "subversion."
Liu Xiaobo was awarded the Peace Prize in 2010 for his activism in support of peaceful democratic change in China, which is under a one-party political system that does not allow criticism.
The case has attracted international headlines and prompted outrage from governments and human rights groups around the world.
On Friday, around 20 protesters gathered in Hong Kong to express support for Liu Xia. Some, including Hang Tung-chow, shaved their heads in solidarity with Liu.
"Using this, 'shave our heads action,' we want to show that we are all Liu Xia. We are all un-free on this land if Liu Xia is un-free."
Beijing has angrily rejected foreign and domestic criticism of the case, insisting it has acted in accordance with its own laws. However, it has not explained why Liu Xia has been held under house arrest.
China's Communist Party-controlled courts have convicted a rising number of activists and dissidents in recent years on subversion or incitement of subversion charges.