Canberra on Friday said it was "deeply disappointed" with the criminal detention of an Australian-Chinese writer in China, demanding Beijing release him if he is being held for "his political views".
Foreign Minister Marise Payne said Australia had received confirmation Friday that Yang Hengjun, held by Chinese authorities since January, had been transferred to criminal detention, apparently on national security grounds.
In a strongly-worded statement, Payne said the government had raised Yang's case repeatedly with Beijing and written twice to Foreign Minister Wang Yi requesting a "fair and transparent" resolution, as well as access for Yang to his lawyer.
"This has not occurred," she said.
"The government has expressed concern about Dr Yang's welfare and the conditions under which he is held," she added.
Payne said she had still not received clarification as to why Yang, also known as Yang Jun, was being held.
"If he is being detained for his political views, then he should be released," she said.
The author and democracy advocate had been held in a secret location since being detained in January shortly after making a rare return to China from his current residence in the United States.
The foreign ministry in Beijing said then he was suspected of endangering "China's national security" -- which often implies espionage allegations.
Until this week he was being held under "residential surveillance at a designated location" (RSDL), a form of detention that allows authorities to hold people for serious crimes.
Payne confirmed Friday that he had been transferred to a criminal detention centre.
Australia has traditionally been keen to avoid friction with its biggest trading partner, but tensions have escalated over security concerns and China's growing presence in the Pacific.
Australia notably angered Beijing when it banned Chinese tech giant Huawei from participating in its 5G network last August over security fears.
Earlier this week Australia challenged China's treatment of its Muslim Uighur minority by calling on Beijing to allow a Uighur woman and her Australian child to leave the country.
Payne's statement on Friday marked a sharp increase in rhetoric over Yang's detention after months of more quiet diplomacy.
"We have worked tirelessly and in good faith with the Chinese government to advocate for Dr Yang's interests since he was detained," she said.
"We expect basic standards of justice and procedural fairness to be met."