He succumbed to cancer in a hospital while remaining under police custody.

Nobel Peace Prize laureate Liu Xiaobo, China’s most prominent political prisoner, died on Thursday at a hospital in the country’s northeast, officials said. He was 61.

Liu had been transferred to the hospital after being diagnosed with advanced liver cancer in prison in May but remained under police custody. In an online announcement, the judicial bureau of the city of Shenyang said he died of multiple organ failure.

Liu was only the second Nobel Peace Prize winner to die in prison, a fact pointed to by human rights groups as an indication of the Chinese Communist Party’s increasingly hard line against its critics. The first, Carl von Ossietzky, died from tuberculosis in Germany in 1938 while serving a sentence for opposing Adolf Hitler’s Nazi regime.

“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.

Liu’s supporters and foreign governments had urged China to allow him to receive treatment abroad, but Chinese authorities insisted he was receiving the best care possible for a disease that had spread throughout his body.

This undated file video grab obtained on July 11, 2017, shows Chinese Nobel Laureate Liu Xiaobo surrounded by doctors and his wife Liu Xia at an undisclosed location. | Photo Credit: AFP

Tiananmen link

Liu was imprisoned for the first time in connection with the 1989 Tiananmen Square pro-democracy protests. He was awarded the Nobel Prize in 2010 while serving his fourth and final prison sentence, for inciting subversion by advocating sweeping political reforms and greater human rights in China.

When the Chinese government sent troops and tanks into Beijing to quash the protests on the night of June 3-4, Liu persuaded some students to leave the square rather than face down the army. The military crackdown killed hundreds, possibly thousands, of people and heralded a more repressive era.

An empty chair without audio equipment where Nobel Peace Prize winner Liu Xiaobo should sit is seen before the Nobel Peace Prize ceremony in Oslo, December 10, 2010. | Photo Credit: Reuters

Liu became one of hundreds of Chinese imprisoned for crimes linked to the demonstrations. It was only the first of four stays in prisons owing to his ideology.

The sentence only increased Liu’s prominence outside of his country.

In 2010, while Liu was serving his sentence in a prison in a small city in China’s northeast, he was awarded the Nobel Prize, with the Norwegian-based committee citing Liu’s “long and non-violent struggle for fundamental human rights in China.”