By the time of the trial, Liu was already China's best-known dissident, and his fame grew even more when he was awarded the Nobel Peace Prize in 2010 while imprisoned in northeast China.
"There should be an independent investigation into the circumstances surrounding Dr Liu's death, his treatment in detention, the timing of the diagnosis of his late-stage liver cancer, and countless other questions that need to be answered, he said".
The commissioner called on Chinese authorities to allow Liu's wife, Liu Xia, the right to travel.
He urged China to lift restrictions on Liu Xia's movements and communications and added, "She and her brother, Liu Hui, should immediately be allowed to leave for Germany or another country of their choice if they wish to".
"The world has failed to save one of the most conscientious and genuine Chinese", said Wu'er, who fled China and now lives in Taiwan.
"Only through democracy, in which every Chinese person has freedom and respect, can China truly become a proud and important country", she said. Nineteen measures were itemized with the aim of improving China's human rights situation.
"The West has bestowed on Liu a halo that will not linger", said an editorial in the state-owned Global Times tabloid.
Those in Japan who knew Chinese Nobel Peace laureate Liu Xiaobo expressed shock Friday at news of his death, saying he was a noble man who dedicated his life to pursuing liberal democratic reform. "They used Liu's illness as a tool to boost their image and demonize China".
It was in May 1989 Xiaobo rose to worldwide prominence when he left his job as a visiting scholar in Columbia University for Beijing to join thousands of students in a protest in Tianenmen Square.
Cruz recalled that Liu's name had been at the top of a list of signatories of Charter 08 - "a manifesto that shined a light on the Communist Party of China and its totalitarian abuse of power". He was the first Nobel Peace laureate to die in state custody since Carl von Ossietzky, the German pacifist and foe of Nazism who won the prize in 1935 and died under guard in 1938 after years of maltreatment.
In Paris on Thursday, French President Emmanuel Macron and his U.S. counterpart Donald Trump praised Chinese President Xi Jinping at a joint press conference, before later issuing statements paying tribute to Liu.
"I'm saddened. It's a huge shock for me", Liu, who is not related to the laureate, said.
Foreign Ministry spokesman Geng Shuang said Beijing lodged official protests with the United States, France, Germany and the United Nations human rights office over their "irresponsible remarks" regarding Liu Xiaobo, and he took aim at his Nobel status.
A drawing of Liu and his wife.
Domestic media outlets, all controlled by the ruling Communist Party, mostly ignored the news, with a photo of a beaming President Xi Jinping meeting his Canadian counterpart dominating the front page of the party mouthpiece the People's Daily.
He said Beijing had prevented Liu from travelling and making a final denunciation of its authoritarian rule to avoid "an enormous public relations disaster ... this one is bad enough".
Xiaobo would spend the next three decades in and out of prison until his death from liver cancer while serving an 11 year sentence for "subversion".