China has told Australia to stop interfering in the case of Chinese-Australian writer, while confirming Yang Hengjun is being held on suspicion of criminal activities.
Foreign Minister Marise Payne has said she is "deeply disappointed" the writer and former diplomat has been transferred to criminal detention.
"If he is being detained for his political views, then he should be released," she says.
But a spokesman for China's foreign ministry says Beijing is carrying out a lawful investigation.
"China's deplores the statement made by the Australian foreign minister and urges the Australian side to stop interfering in the handling of the case by the Chinese side and stop issuing irresponsible remarks," the spokesperson said in a statement obtained by AAP.
The Chinese-born fiction writer, pro-democracy campaigner and former diplomat was being held in Guangzhou after arriving from the US in January.
The 53-year-old, who has held Australian citizenship since 2002 and has a doctorate from the University of Technology Sydney, was living in New York as a visiting scholar at Columbia University.
Australian officials have visited Dr Yang in detention six times, most recently on June 27.
But Senator Payne said despite writing twice to her Chinese counterpart asking for a fair and transparent resolution and for Dr Yang to be allowed to see his lawyers, that had not happened.
"We expect basic standards of justice and procedural fairness to be met."
China's statement said the Beijing State Security Bureau has taken compulsory measures and investigated him according to law.
"The Chinese authority will handle the case in strict accordance with the law and fully protect his legal rights," the spokesperson said.
Australian lawyer Rob Stary said a political intervention was the only likely means by which to resolve the issue.
He says Australia should use its special relationship with China to secure Dr Yang's release.
Dr Yang's wife, Yuan Xiaoliang, who is a permanent resident of Australia, has been banned from leaving China.
The Law Council of Australia strongly supports Senator Payne's remarks and intervention in this "very troubling matter".
"The Law Council remains concerned that Dr Yang does not appear to have the benefit of any of the traditional safeguards expected of an independent criminal justice system and the rule of law," it said in a statement on Saturday.
This included access to a lawyer of his choice, the right for the public to know what he is being detained for and when it is expected that he will be released.
Australian Associated Press