BEIJING -- Chinese Nobel Peace Prize laureate Liu Xiaobo's health is further deteriorating as his liver function worsens and abdominal fluid accumulates, a friend and the hospital that is treating him said, adding to concerns about the long-term prognosis for the country's best-known political prisoner.

The doctor heading a medical team in charge of Liu's treatment for late-stage liver cancer informed his family of the development, the First Hospital of China Medical University said in a statement that appeared on its website Thursday.

A family friend confirmed on Thursday that Liu's family had been asked to be on standby in the hospital in the northeastern city of Shenyang over the next 24 hours -- which they took as a sign that Liu is critically ill.

"We are worried about whether we should start planning for what to do after he leaves," family friend Wu Yangwei, better known by his penname Ye Du., told The Associated Press.

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Wu on Thursday shared on social media an undated photo of a visibly emaciated Liu, in blue-and-white-striped hospital pajamas, embracing his wife Liu Xia, who gazed up at his expressionless face. The photo appeared to have been taken at the hospital, though its background seemed to have been digitally blurred.

Liu's liver function is deteriorating, the hospital said in a separate statement later Thursday. The hospital said doctors detected increasing levels of a natural waste product called bilirubin in Liu's body -- a sign that his liver is not effectively filtering the byproduct from his blood. Elevated bilirubin levels are linked to jaundice.

The hospital also said there were signs that Liu might have blood clots in his lower left leg. Clots are most dangerous when they travel to the lungs, a potentially life-threatening situation, or to the brain, where they can cause a stroke.

Liu was diagnosed in May while serving a 11-year sentence for inciting subversion by advocating sweeping political reforms that would end China's one-party rule. He was awarded the Nobel Peace Prize in 2010, a year after his conviction.

Since the diagnosis was made public in late June, his supporters, Western governments and human rights groups have been urging Beijing to release Liu and give him the freedom to choose where he wants to be treated. Beijing has maintained that this is an internal affair other countries should stay out of and that Liu is under the care of experts in the Chinese medical facility.

Guo Yuhua, a professor of sociology in Beijing, said the government has failed to give Liu what he most needs.

"Liberty, family and friendship are the best medicine, yet Beijing would never offer them to him," she said.

Maya Wang, a researcher for Human Rights Watch, called Liu's treatment "shameful."

"The Chinese government's treatment of Liu Xiaobo, which includes holding him and his family even in his dying days, reveal the cruelty and ruthlessness of the Chinese government," Wang said. "How can such a government be considered as a reliable and responsible partner for global leadership?"

The hospital statement also included the names of some of the experts, including Dr. Mao Yilei, a reputed expert on liver cancer at the prestigious Peking Union Medical College Hospital, who conducted another round of group consultations on the day when the statement was released, which was most likely Thursday.

In a likely response to criticism that China might have failed to adequately care for Liu, the statement said the experts were approving of prior treatments of Liu. They also adjusted the treatment as Liu's illness developed, the hospital said.

On behalf of the medical team, Mao informed Liu's family of his most recent condition, and Liu's family said they understood, the statement said. The statement was impossible to verify with Liu's wife or other family members, who have not been contactable and are said to face restrictions on their movements and communications with the outside world. Calls to the hospital were unanswered on Thursday.