Originally posted by the Voice of America. Voice of America content is produced by the Voice of America, a United States federal government-sponsored entity, and is in the public domain. Rights Groups, Nobel Commission Express Regret Over Liu's Death by VOA News U.S. Secretary of State Rex Tillerson is calling for China to release Liu Xiaobo's widow from house arrest Thursday. "I call on the Chinese government to release Liu Xia from house arrest and allow her to depart China, according to her wishes," he said in a statement hours after the Nobel Laureate's death. "In his fight for freedom, equality, and constitutional rule in China, Liu Xiaobo embodied the human spirit that the Nobel Prize rewards. In his death, he has only reaffirmed the Nobel Committee's selection," Tillerson added. Liu, a Chinese a literary critic-turned-dissident and pro-democracy advocate, died Thursday at age 61 following a high-profile battle with liver cancer. The leader of the Norwegian Nobel committee said Thursday the Chinese government bore a "heavy responsibility" 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-Anderssen. "The Chinese Government bears a heavy responsibility for his premature death," she said in an emailed statement. Rights groups were quick to praise his achievements and legacy while calling on the international community to investigate deaths in captivity and work to prevent them. "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," said Sophie Richardson, China director for Human Rights Watch. "The Chinese government's arrogance, cruelty, and callousness are shocking -- but Liu's struggle for a rights-respecting, democratic China will live on." The U.N. Human Rights Chief expressed "deep sorrow" over Liu's death, saying the human rights movement has lost a "principled champion". House minority leader Nancy Pelosi also expressed her condolences for Liu and disappointment with the Chinese government's handling of his illness. "The world grieves loss of one of the great moral voices of our time. We had hoped that the Chinese ... they mistreated him in prison, contributed to his illness, we would hope that they would allow him to leave the country to receive medical care," she said, "They did not. It is a sad day."