Yang Hengjun, who retired from the Chinese Foreign Ministry to become a Sydney-based spy novelist, intellectual and blogger, has not been seen since phoning a colleague from Guangzhou airport on Sunday with news that he was being followed by three men.
If Dr Yang does not promptly reappear then his name will be added to the list of challenges facing Julia Gillard when she arrives in Beijing next month for her first visit as Prime Minister.
Mr Yang is understood to carry an Australian passport.
Others on the PM's list of Australians who have fallen foul of China's justice system include Matthew Ng, one of Australia's most successful entrepreneurs in China, and Australian iron ore salesman Stern Hu.
Mr Ng also disappeared in Guangzhou before being charged with embezzlement. Mr Hu, the Rio Tinto executive, was sentenced a year ago to 10 years' jail for taking bribes and receiving commercial secrets.
Dr Yang is considered to be ''the most influential political blogger in China, with millions of readers," according to Feng Chongyi, who supervised Dr Yang's PhD thesis at the University of Technology, Sydney.
Friends and colleagues told The Age they believed Dr Yang was the latest and most prominent victim of Beijing's response to the "jasmine revolutions" that have swept the Middle East.
"In a little over a month dozens of people have been detained and about half a dozen or more prominent people have simply disappeared, without a trace and without any hint of legal procedure being followed," said Joshua Rosenzweig, research director for the Dui Hua Foundation, a human rights group in Hong Kong.
"I haven't seen anything of this scope since the late 1990s," he said.
Dr Yang was known in China for his ability to communicate with Chinese officials as well as intellectuals, journalists and activists.
He was one of the few prominent signatories of the Charter 08 democratic manifesto who was not called in "to have tea" with security officials.
Dr Yang studied at Shanghai's Fudan University under Wang Huning, a foreign policy expert who accompanies on President Hu Jintao on almost every overseas trip.
In recent days Dr Yang has criticised a new surveillance system at Peking University aimed at identifying potentially "radical" students. He also lamented the burden facing China's intellectuals after the dissident Liu Xianbin was sentenced last Friday to 10 years in prison for inciting subversion.
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