Foreign Minister Marise Payne said she was “concerned and disappointed” that Yang Hengjun, a Chinese native who’s now an Australian citizen, would “continue to be criminally detained”.

“It is important, and we expect, that basic standards of justice and procedural fairness are met,” Payne said in a statement Tuesday. “I respectfully reiterate my previous requests that if Dr Yang is being held for his political beliefs, he should be released.”

Yang was detained in the southern city of Guangzhou in January after a flight from New York.

His lawyer Rob Stary told the Australian newspaper on Tuesday that the precise nature of the espionage allegations were not clear, though it apparently relates to his “democracy activism.”

China’s Ministry of Foreign Affairs didn’t immediately respond to a request for comment.

At the time of his detention, the Foreign Ministry in Beijing said Yang was being investigated for “criminal activities endangering national security”.

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

Payne said Yang had been held in “harsh conditions” without charge and denied access to lawyers or his family. She said she had discussed the issue twice with her Chinese counterpart and written to him three times raising her concerns.

Yang has been visited by embassy officials seven times since his detention and a visit is scheduled for today, she said.

“I will continue to advocate strongly on behalf of Dr Yang to ensure a satisfactory explanation of the basis for his arrest, that he is treated humanely and that he is allowed to return home,” Payne said.