The following content is sourced from external partners. Family and friends, as well as foreign governments and organizations, had been petitioning the Chinese government to allow him to go overseas for treatment.
U.S. Secretary of State Rex Tillerson and United Nations rights chief Zeid Ra'ad Al Hussein also called on the Chinese government to release Liu Xia from house arrest and allow her to leave the country.
Mr Reiss-Andersen also paid tribute, saying: "Liu Xiaobo received the Nobel Peace Prize for 2010 for his efforts to implement the fundamental human rights secured in global instruments as well as in the constitution of the People's Republic of China".
His most recent prison sentence stemmed from his co-authorship of Charter 08, a manifesto calling for political reform and human rights in China.
The legal bureau in the northeastern city of Shenyang said on its website that Liu succumbed to multiple organ failure, three days after being taken into intensive care at the First Hospital of China Medical University.
"I feel a lot of sadness and hatred, but now we have to focus on Liu Xia", friend and fellow activist Mo Zhixu told dpa after learning about Liu's death.
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The Norwegian government, which resumed full diplomatic relations with Beijing in December after they were put on ice due to the Nobel award to Liu Xiaobo, said in a one-paragraph statement it was saddened by Liu's death.
Liu was a "giant of human rights" who for decades "fought tirelessly to advance human rights and fundamental freedoms in China", he added.
"It is a sad and disturbing fact that the representatives of the free world, who themselves hold democracy and human rights in high regard, are less willing to stand up for those rights for the benefit of others", she said. "But the Communist regime was so cruel toward Liu Xiaobo because its leaders knew, in their hearts, the power of his message", he said.
China's state news agency Xinhua reported Liu's death in a brief story in English, but not Chinese. "He was a writer, an intellectual and he used his life to find ways to make society better".
"The Chinese government's arrogance, cruelty, and callousness are shocking - but Liu's struggle for a rights-respecting, democratic China will live on", Sophie Richardson, the China director at Human Rights Watch, said in a statement.