Nobel laureate Liu Xiaobo, China's most famous political prisoner, died in custody at the age of 61.

His death was confirmed this evening by authorities at a northeastern China hospital where he was treated for liver cancer in an isolated ward under armed guard, The Guardian reported.

He is the first Nobel prize winner to die in custody since German pacifist and 1935 prize winner Carl von Ossientzky.

The Norwegian Nobel Committee, which awards the Nobel Peace Prize blames the Chinese government for his death.

"We find it deeply disturbing that Liu Xiaobo was not transferred to a facility where he could receive adequate medical treatment before he became terminally ill," said Berit Reiss-Andersen.

"The Chinese Government bears a heavy responsibility for his premature death," she told Reuters in an emailed statement.

Liu served an 11-year sentence for involvement in a pro-democracy manifesto called Carter 08, which called for the end of China's one-party rule.

A lifelong activist, he spoke out for democracy despite two stints behind bars.

He returned to Beijing from New York, where he was working in 1989 during the pro-democracy protests and decided to stay and contribute to the movement.

He led hunger strikes during the Tiananmen Square protests and was jailed for two years for his alleged role in anti-establishment riots.He had two more stints behind bars after that but continued to speak out against authoritarianism through interviews and his writings.