China faced growing calls on Tuesday to immediately release Liu Xiaobo, the country's only Nobel Peace Prize winner imprisoned since 2009, following the revelation of his serious cancer diagnosis.

His wife, Liu Xia, was seen in a video clip posted on Twitter speaking to a friend on a mobile phone about his dire medical condition.

"(He) could not have surgery, could not have radiotherapy, could not have chemotherapy," she said in tears in the clip, whose recording date could not be verified.

The famed dissident's lawyer Mo Shaoping confirmed Monday that the 61-year-old, who has been jailed for his writings advocating greater democracy, was recently taken from prison to a hospital in the northeastern Chinese city of Shenyang.

Liu and his wife, who has been under house arrest in Beijing without trial since his being awarded the Nobel Prize in 2010 in absentia, were allowed to meet at the hospital, one of their relatives told Kyodo News.

The U.S. Congressional Executive Commission on China urged Liu's immediate transfer with his wife to the United States for treatment and sought medical paroles for other detained Chinese dissidents facing serious health issues.

"Even with (the news that Liu) has been released from prison for medical treatment, serious questions remain," commission chairman Sen. Marco Rubio said in a statement.

Rubio questioned, "How long have Chinese authorities known of his grave health condition? What are the terms of his medical parole? Will his wife, Liu Xia, be able to permanently oversee his care or will she remain under house arrest, where her own health has been a serious concern?"

Asked if China would consider letting Liu to receive treatment abroad, Chinese Foreign Ministry spokesman Lu Kang, speaking at a press briefing said, "We have repeatedly said that no country has any right to tell China what to do about its internal affairs."

Still, when Chinese President Xi Jinping and other leaders of the Group of 20 major economies meet next week in Germany for this year's summit, there is a possibility that the issue of Liu will be raised.

Liu, a literary critic and university lecturer, was sentenced to 11 years in prison in December 2009 for "inciting subversion of state power" by helping draft a blueprint for political change, known as Charter 08, calling for democracy, human rights and the rule of law in China.

Chinese mainland media have no reports on the latest situation of Liu.

But in Hong Kong, about 70 people demonstrated at the Central Government Liaison Office, Beijing's representative in the territory, demanding the release of Liu and freedom for his wife.

"We demand the best medical treatment for Liu Xiaobo," said Cheung Man-kwong of the Hong Kong Alliance in Support of Patriotic Democratic Movements of China. "We hope our concerns can bring Liu the best care and even an extension of his life."

In a petition letter, hundreds of the signatories of the Charter called for the unconditional release of Liu and his wife, the release of his health records while in prison, and an investigation into the cause of his deteriorating health as well as those responsible for his late treatment.

Writer Ye Du, one of the signatories, posted on Twitter that Liu is receiving targeted treatment for cancer but the cancer cells have spread and his condition is not optimistic.

The prison administration bureau in the Chinese province of Liaoning confirmed Monday on its website that Liu was granted medical parole in recent days and is being treated by cancer specialists at the First Hospital of China Medical University in Shenyang.

But there was no official record of Liu's admission to the hospital, where security measures were lax, Hong Kong's Cable TV reported.