SYDNEY (REUTERS, BLOOMBERG, AFP) - Australian writer Yang Hengjun has been formally arrested in China on suspicion of espionage and is being held in “harsh conditions”, the Australian government said on Tuesday (Aug 27).

Yang, who was born in China, was detained in the southern city of Guangzhou in January amid growing tension between Australia and its largest trading partner.

“We have serious concerns for Dr Yang’s welfare, and about the conditions under which he is being been held,” Australian Foreign Minister Marise Payne said in a statement.

China’s near-silence about Yang’s fate has been a point of friction in relations with Australia that have markedly deteriorated in recent months.

In a sharply worded statement, Ms Payne said she had raised the case five times with her Chinese counterpart Mr Wang Yi, in person and via letters.

“Dr Yang has been held in Beijing in harsh conditions without charge for more than seven months,” she added. "Since that time, China has not explained the reasons for Dr Yang’s detention, nor has it allowed him access to his lawyers or family visits.”

Beijing said Tuesday that Canberra should not “intervene” in China’s judicial processes after confirming Australian national Yang Jun had been arrested for alleged espionage.

“I would like to emphasise that China is a country ruled by law and the Australian side should earnestly respect China’s judicial sovereignty and must not intervene in any cases handled in China,” said China's foreign ministry spokesman Geng Shuang.

Yang, 53, whose legal name is Yang Jun, was detained in China while waiting for a transfer to Shanghai, after flying in from New York.

Yang's lawyer Rob Stary told the Australian newspaper he had been informed of the charges by Australia's Department of Foreign Affairs and Trade (DFAT).

"They don't specify what the espionage relates to," the Australian cited Stary as saying.

"But we are told it is espionage and it relates to his democracy activism."

Yang previously was a Chinese foreign affairs official in Beijing, before becoming an Australian citizen and novelist, the Australian newspaper reported earlier this year.

He had used popular blog and social media posts to criticise Beijing’s authoritarian government. He has a following of more than 125,000 on Twitter alone.