Chinese-Australian writer Yang Jun, who was handed a suspended death sentence in China, had gained a huge following in exile for his spy novels and calls for greater freedom in his homeland.
Yang -- who also goes by the pen name Yang Hengjun -- was born in China in 1965 and became an Australian citizen in the early 2000s.
He grew a readership in exile as the author of novels that drew on his experiences in his homeland.
He said he once worked for the Chinese foreign ministry, although Beijing has denied that.
Yang had a following of more than 125,000 on Twitter at the time of his arrest, frequently sharing calls for more openness and freedom in China.
In a 2021 letter from prison, Yang said it was still unclear who he is accused of spying for.
"This isn't a crime of ideology. The charges are about espionage. But who did I work for? If this is a crime, and if I'm a criminal, then who did I work for? I didn't work for Australia or the US," he wrote.
"I'm only writing for people. Writing for rule of law, democracy, and freedom."
Yang's family say his health has deteriorated in prison and that they are fearful he will be "left to die".
He was formally detained on espionage charges in 2019 while on a rare return to China from the United States, where he was living at the time.
Canberra said the claim he had acted as a spy for Australia was "absolutely untrue".
It was not the first time that Yang vanished in China: he went missing during a 2011 trip but resurfaced days later, describing his disappearance as a "misunderstanding".
No such release was forthcoming this time around, however, and a closed-doors trial was held in Beijing in 2021, although no verdict has yet been made public.
Officials have not provided details of Yang's alleged spying, which Beijing defines broadly and for which it metes out harsh punishment, from life in prison to execution in extreme cases.
The writer has insisted he is "100 percent innocent".
Yang previously told supporters he was tortured while at a secret detention site and that he feared forced confessions may be used against him.
Writing from prison in 2019, Yang pleaded to Canberra to put aside its economic reliance on China to help him go home.
A Chinese investigator "told me that Australia was small and wouldn't care about me", Yang said in the letter, obtained by national broadcaster ABC.
"He said Australia was dependent on China for its trade and economy, and Canberra wouldn't help me, let alone rescue me. He said Australia wouldn't help because I am not white.
"This is nonsense. He was wrong," he said.
Beijing's foreign ministry has insisted that Yang's rights are being respected and accused Canberra of interference.
Yang's sons counter that he is being held in dire conditions.
They say he is being subject to "particularly cruel" treatment -- deprived of his beloved books in a cramped cell in which he must "eat, drink, defecate and urinate".
They urged Australian Prime Minister Anthony Albanese last November to raise their father's plight during his first official visit to Beijing. Albanese promised he would.
The release of fellow Chinese-Australian journalist Cheng Lei the previous month after a three-year detention had left them hoping for a "second miracle", they said.
"Like Cheng Lei, our father cherishes the freedoms and protections that come with his Australian identity," Yang's sons said in a letter.
But no such miracle has occurred, with Australia's top diplomat Monday describing news of Yang's sentence as "harrowing".
"We will not relent in our advocacy," she promised.
