Yang, a pro-democracy blogger, is an Australian citizen born in China who was working in New York before his arrest at Guangzhou airport in 2019. He had been accused of spying for a country China has not publicly identified and the details of the case against him have not been made public.
Sydney based scholar Feng Chongyi said a court on Monday delivered a suspended death sentence that would convert to life imprisonment after two years.
It was a "serious case of injustice", he said, adding that Yang had denied the charges. He urged the Australian government to seek medical parole for Yang.
Yang's sentence was confirmed by another human rights lawyer in Beijing who has been following his case.
"He was found guilty of all charges," the lawyer said, asking to remain anonymous because of the sensitivity of the matter.
Australia is "appalled" at the court's decision and has called in China's ambassador, Australian Foreign Minister Penny Wong said on Monday.
Wong said in a statement on Monday the Australian government understood the sentence can be commuted to life imprisonment after two years if the individual does not commit any serious crimes in that period.
"This is harrowing news for Dr Yang, his family and all who have supported him," she said.
Yang's family was "shocked and devastated by this news, which comes at the extreme end of worst expectations", said a family spokesman in Sydney.
Australia had said it was troubled by repeated delays in Yang's case, and had advocated for his well-being, including access to medical treatment "at the highest levels".
The Chinese foreign ministry did not immediately respond to a Reuters request for comment.
A Beijing court heard Yang's trial in secret in May 2021 and the case against him has never been publicly disclosed. He has denied working as a spy for Australia or the United States.
Yang wrote about Chinese and U.S. politics as a high-profile blogger and also wrote a series of spy novels before his detention.
His two sons, who live in Australia, wrote to Prime Minister Anthony Albanese in October on the eve of his visit to Beijing, urging him to seek Yang's release on medical grounds.
"The verdict casts a shadow over bilateral ties and will for some time, as it acts as a potent reminder of the opacity of the Chinese system and its imperviousness to reasonable foreign complaints," said Richard McGregor, senior fellow at the Lowy Institute in Sydney.
His supporters have argued Yang should be released on medical parole, and he was told last year he had a 10 cm (4 inch) cyst on his kidney that may require surgery.
Yang was detained as Australia-China ties deteriorated in 2019, and hopes of his release had been raised by the release of Australian broadcaster Cheng Lei shortly before Albanese visited China last year.
James Laurenceson, Director of the Australia-China Relations Institute at University of Technology, Sydney, said that Beijing had said it wanted to move beyond the stabilisation of ties with Australia, but that the sentence would make a thaw harder.
"This decision makes it extremely difficult for the Albanese government to do so in terms of managing the domestic politics. The strong language already used by foreign minister makes plain their disappointment," he said.
