(CNN) A university professor known for being an open critic of Chinese President Xi Jinping has allegedly been fired from his job at a top Beijing university, according to two people with knowledge of his situation.
Xu Zhangrun had been teaching law at Tsinghua University, one of China's most prestigious tertiary education institutions, until he was suspended and put under investigation in March 2019 following the publication of an essay criticizing Xi's concentration of power and crackdown on dissent.
Journalist Gao Yu, a friend of Xu's, confirmed the former professor had been dismissed by Tsinghua, although she didn't know when the decision had been made.
CNN agreed not to report the name of the other source, who has been in touch with people close to Xu's family, because the source feared retribution from authorities.
Tsinghua University has yet to publicly comment on the situation. CNN has contacted the university's publicity department Tuesday for further comment.
Xu confirmed the reports in an interview with Hong Kong public broadcaster RTHK published Tuesday. According to RTHK, he said he was being punished by the university for "corrupted morals," and that he will not appeal the decision.
Xu did not immediately respond to CNN's request for comment.
Xu's alleged dismissal appears to be the latest example of increasing censorship and restrictions on academic freedoms in China under Xi, whose administration has cracked down on dissenting voices
Despite the risks to his career and his personal freedom, Xu has frequently criticized the Chinese government and Communist Party leadership in recent years.
In 2018, Xu published a lengthy essay in response to the decision by the Communist Party to remove presidential term limits, effectively allowing Xi Jinping to remain in power indefinitely.
"Suddenly, as if out of nowhere, we had a 'supreme leader' with no checks on his power; how could people not have all kinds of strange imaginings and new fears?" Xu asked in his essay.
His suspension from Tsinghua in 2019 did not stop Xu from criticizing the Chinese government. In an essay published in February 2020, amid China's coronavirus outbreak, Xu blamed Xi, who the author refers to as 'The Axle,' "and the cabal that surrounds him" for the crisis.
"The political life of the nation is in a state of collapse and the ethical core of the system has been rendered hollow," Xu wrote. The essay was initially published in Chinese by Matters, a news and commentary site popular with liberal intellectuals that is banned in China. It was translated into English with Xu's permission by China scholar Geremie Barme.
On July 6, police officers arrived at Xu's Beijing home and took him into custody, according to the two sources. Gao said the former professor was held for six days before being released on Sunday.
"He's resting at home. So far there is no more information available (on his case)," Gao said.