Beijing on Tuesday pushed back against claims from Canberra that a detained Australian writer was being arbitrarily held and not receiving adequate medical support despite his declining health.

Chinese-born Australian Yang Jun has been accused by Beijing of espionage and is facing a trial which started last year behind closed doors.

But the Australian foreign minister said in a radio interview that Yang was being held arbitrarily, and that Canberra was increasingly concerned about his well-being.

"We are concerned about his health and we've been consistently clear that he needs to be provided with the necessary treatment for both his physical and his mental health," Marise Payne said Tuesday.

In response to Payne's comments, China's foreign ministry said the case was being handled "in strict accordance with the law."

"All legal rights and interests of Yang Jun have been fully protected," said foreign ministry spokesman Zhao Lijian at a press briefing.

"We firmly oppose the Australian side's unjustifiable disruptions to the handling of the cases in accordance with the law and the gross interference in China's judicial sovereignty."

Chinese-born Australian writer Yang Jun has been accused by Beijing of espionage and is facing a trial which started last year behind closed doors
Chinese-born Australian writer Yang Jun has been accused by Beijing of espionage and is facing a trial which started last year behind closed doors AFP / NICOLAS ASFOURI

Yang, who denies the charges, was arrested on a rare return to China from his home in the United States in January 2019.

The writer and academic -- who also goes by his pen name Yang Hengjun -- has previously told supporters he was tortured while at a secret detention site and fears forced confessions may be used against him.

Elaine Pearson, Australia director for Human Rights Watch, wrote on Twitter that three years of detention in China "has exacerbated Yang Hengjun's medical problems & treatment in prison is inadequate."

She added that there was a "long list of human rights defenders who have died in Chinese custody or shortly after being released."

Yang is one of at least two Australians currently being detained in China, with TV anchor Cheng Lei having been held since August 2020.

Relations between the two countries have sharply deteriorated in recent years with disputes over everything from telecoms giant Huawei to the origins of Covid-19.