China’s most prominent human rights and democracy advocate, Liu Xiaobo has died at the age of 61, BBC reported. The Nobel Peace Prize winner had been diagnosed with liver cancer in May. The judicial bureau in Shenyang city told AP that Liu died of multiple organ failure.

Liu had been granted medical parole in June. He was being treated in an isolated ward under an armed guard in a hospital in north-eastern China, according to The Guardian.

Liu was serving an 11-year sentence for writing a pro-democracy manifesto called Charter 08, where he called for an end to one-party rule in China. He had been jailed multiple times throughout his life. His wife had also been placed under house arrest. Liu had to face heavy restrictions even when he was free.

German Chancellor Angela Merkel, Taiwan President Tsai Ing-wen and other world leaders had urged China to allow Xiaobo to travel overseas to receive medical care, but Beijing had refused.