Chinese activist Liu Xiaobo passed away from multiple organ failure on Thursday after struggling with late-stage liver cancer, according to the justice bureau in Shenyang.

The hospital in the northeastern city where Liu was being treated said the dissident had suffered respiratory failure on Wednesday. His family rejected artificial ventilation, according to medical officials.

Read more: Liu Xiaobo, China's dissident 'without enemies'

Sixty-one-year-old Liu was the co-author of a document known as "Charter 08" which called for a free, democratic and constitutional state in China. The charter was signed in 2008 by more than 300 Chinese intellectuals. Chinese authorities arrested Liu a year later and sentenced him to 11 years in prison for "inciting subversion of state power." He was awarded the Nobel Peace Prize in absentia in 2010.

He was diagnosed with terminal liver cancer in May and released on medical parole two weeks ago. Two cancer specialists from Germany and the US examined Liu on Saturday and said he could be moved abroad for treatment. However, the hospital said it would be "unsafe" for the patient to travel.

Tributes pour in

Chinese dissident artist Ai Weiwei, a lonstanding friend of Liu's, told DW that his death was a severe blow "because the human rights movement in China is already in a very, extremely sad condition." 

"I think Liu Xiaobo's legacy is, despite such impossible conditions, still that of an individual who was intelligent, brave, and had strong hope for humanity. And one who believed, through those individuals defending, that they can win," Ai told DW. "Last time I heard from his is right before he went to jail. He sent me the Charter 08, the reason why he has been sentenced. He asked me my opinions on that writing." 

German Chancellor Angela Merkel expressed her deep condolences for Liu's family, while her foreign minister Sigmar Gabriel called for China to allow Liu's wife and her brother to leave for Germany or any other country.

"I mourn for Liu Xiaobo, the courageous fighter for civil rights and freedom of expression." Merkel had earlier appealed for China to show "humanity" in his case.

Gabriel said Liu and his wife Liu Xia had wanted to come to Germany.

"China now has the responsibility to quickly, transparently and plausibly answer the question of whether the cancer could not have been identified much earlier," Gabriel said.

German Justice Minister Heiko Maas hailed Liu as a "hero.""His non-violent resistance made him a hero in the battle for democracy and human rights. RIP," Maas wrote on Twitter. 

Frank-Walter Steinmeier, who holds Germany's largely-symbolic presidency, also offered his condolences. He said Liu "only wanted the best for his country and will not be forgotten."

The leader of Germany's Social Democrats, Martin Schulz, said "we lose a strong voice for freedom and democracy. He resisted all reprisals. A great role model!"

United Nations human rights chief Zeid Raad Al Hussein expressed his deep sorrow, saying Liu "will continue to be an inspiration for all human rights defenders. He called for China to allow his wife to travel abroad.

French Foreign Minister, Jean-Yves Le Drian, expressed sadness over the death and called on Chinese authorities to allow his wife and family to move around freely.

"Despite long periods of detention and for more than 30 years, he never stopped defending, with courage, fundamental rights and freedom of speech," Le Drian said in a statement.

Amnesty International said his death should trigger a deeper focus on China's human rights abuses.

"For decades, he fought tirelessly to advance human rights and fundamental freedoms in China," Salil Shetty, Secretary General of Amnesty International said in a statement. 

"He did so in the face of the most relentless and often brutal opposition from the Chinese government. Time and again they tried to silence him, and time and again they failed. Despite enduring years of persecution, suppression and imprisonment, Liu Xiaobo continued to fight for his convictions.

"Although he has passed, everything he stood for still endures. The greatest tribute we can now pay him is to continue the struggle for human rights in China and recognize the powerful legacy he leaves behind. Thanks to Liu Xiaobo, millions of people in China and across the world have been inspired to stand up for freedom and justice in the face of oppression."

Chinese government condemned

Human Rights Watch said Liu's death laid bare "the Chinese government’s ruthlessness toward peaceful proponents of human rights and democracy.

"Even as Liu Xiaobo’s illness worsened, the Chinese government continued to isolate him and his family, and denied him freely choosing his medical treatment," Sophie Richardson, China director, said in the statement. "The Chinese government’s arrogance, cruelty, and callousness are shocking – but Liu’s struggle for a rights-respecting, democratic China will live on."

The organization called for an international inquiry into his death in custody and called for his wife to be released.

Berit Reiss-Anderssen, the leader of the Nobel Peace Prize committee which recognized Liu in 2010, said he had committed no crimes and said the Chinese government held a heavy responsibilty for his death.

"(Liu) will remain a powerful symbol for all who fight for freedom, democracy and a better world," Reiss-Anderssen said.

Fellow dissidents try to visit

Friends of the dissident had made their way to Shenyang on Wednesday to be at his side, despite fears of being arrested.

Documentary filmmaker Zeng Jinyan told The Associated Press on Wednesday she and a fellow supporter drove eight hours from Beijing, but were unable to see the closely-guarded patient.

"By coming to Shenyang from Beijing, we're just trying to get closer to Xiaobo and Liu Xia, trying to be with him as he goes through this rough time," Zeng said in an interview in a nearby hotel room.

On Thursday, many plainclothes security agents were seen stationed at the hospital's entrance and inside the crowded facility.

"I'm sorry, Xiaobo. I'm sorry. We put forth our greatest effort, but we could not win your freedom while you were still living," Liu's friend and Beijing-based dissident Hu Jia said on Twitter. 

"But we will continue fighting for freedom for your love Liu Xia. The world is sorrowful. Your unfulfilled wish is our mission."

Internationally acclaimed artist and activist Ai Weiwei told Reuters it was a difficult time for Chinese human rights defenders.

"He was a writer, an intellectual and he used his life to find ways to make society better," Ai said from his Berlin studio.

Asked whether the Chinese government had contributed to Liu's death by preventing him from receiving treatment for late-stage liver cancer abroad, Ai said: "China showed how brutal its society can be."

Calls for release of wife

His wife, Liu Xia, was placed under house arrest in 2010, but was allowed to see him at the hospital. Human rights groups had urged the government to free her alongside Liu Xiaobo.

Wang Dan, a prominent leader of the 1989 Tiananmen Square protests, tweeted that governments and people worldwide must press for Liu Xia to be allowed to leave China, where she has been held under extralegal house arrest.

Wang wrote, "Xiaobo, my beloved teacher, my dear brother, you accepted too much hardship, rest easy."

The UN human rights chief said "I urge the Chinese authorities to guarantee Liu Xia’s freedom of movement, and allow her to travel abroad should she wish so."

US Secretary of State Rex Tillerson called on China to free Liu's widow.

"Mr Liu dedicated his life to the betterment of his country and humankind, and to the pursuit of justice and liberty," Tillerson said in a statement.

US ambassador to China Terry Branstad said: "China has lost a deeply principled role model who deserved our respect and adulation, not the prison sentences to which he was subjected" and called on Beijing to release all prisoners of conscience.

British Foreign Secretary Boris Johnson said in a statement: "Liu Xiaobo should have been allowed to choose his own medical treatment overseas, which the Chinese authorities repeatedly denied him."

His death means Liu is the first Nobel Peace Prize laureate to die in custody since German pacifist Carl von Ossietzky, who passed away in a hospital while held by the Nazis in 1938.

"Hitler was wild and strong and thought he was right - but history proved he was wrong in imprisoning a Nobel Peace Prize winner," said Mo Shaoping, an old friend and Liu's former lawyer, adding that he was heartbroken by Liu's death. "The authorities consider Liu Xiaobo guilty, but history will prove he is not."

His death in custody followed the March 2014 death of activist Cao Shunli in a Beijing hospital, and the July 2015 death of Tibetan lama Tenzin Delek who died in detention after being jailed for alleged separatist activity.

The Chinese government made no immediate official comment on Liu's death, although state broadcaster CCTV issued a brief statement on
its English-language website.

CCTV said Liu had been "jailed for engaging in activities designed to overthrow the Chinese government."

"Liu was sentenced to 11 years in jail on December 25, 2009, after a local court in Beijing convicted him of agitation aimed at subverting the government," it said.

aw/rt (AP, dpa, AFP, Reuters)