Chinese author Mo Yan, the winner of the 2012 Nobel Prize for Literature, stopped short of supporting a petition signed by fellow laureates calling for the release of Nobel Peace Prize winner Liu Xiaobo.

Mo, the first “acknowledged” Chinese national to be awarded the prize, refused to express support for Liu and insisted that he had always been “independent” when asked on whether he would support the laureates’ petition. He has drawn criticism from dissidents and other writers.

The author, best known in the West for “Red Sorghum”, said that censorship was sometimes necessary and compared it to security checks at airports while in Stockholm to receive the award.

“I have never praised a system of censorship, but also censorship exists in every country,” he said during the news conference on Thursday. “There is only a difference of a degree of censorship.”

“I have said this prize is about literature. Not for politics,” Mo said.

Hu Jia, one of China’s most prominent dissidents, told Reuters he was “very disappointed” while some writers claimed Mo was “unworthy of winning.”

A group of 134 Nobel laureates, including the Dalai Lama and Desmond Tutu, wrote to Chinese Communist Party chief Xi Jinping urging him to release Liu and his wife.