A prominent Chinese-born academic at a Sydney university was stuck in southern China on Monday after being prevented from flying home to Australia, according to his lawyer.
Police last Friday blocked Feng Chongyi, a permanent resident of Australia, from boarding a flight for Sydney from Guangzhou's international airport, lawyer Liu Hao told AFP.
"They told Feng that... he was suspected of harming national security and could not leave China," Liu said.
"They didn't show any ID or papers. They just held him for questioning at the airport before releasing him."
Feng teaches at the University of Technology Sydney (UTS). Formerly he was head of Chinese Studies at UTS for 11 years and conducted research on China's pro-democracy groups.
More recently the former newspaper publisher has criticised Beijing's influence on Australia's Chinese-language media outlets.
Feng is staying in a hotel in Guangzhou and does not know when he will be able to return to Sydney, sources told AFP.
The impasse overshadowed a five-day visit by Chinese Premier Li Keqiang to Australia, which ended Sunday, to promote economic ties.
Former Australian foreign minister Bob Carr, who leads the Australia-China Relations Institute at UTS, was in China attending the Boao economic forum over the weekend.
Carr said in a statement Monday that he was "making representations in Beijing and Canberra about the case" and "hoped Dr Feng's return could be quickly resolved".
Australia is aware that a UTS professor has been prevented from leaving China but the government can provide consular assistance only to "citizens who have entered China on their Australian passport", the Department of Foreign Affairs and Trade told AFP.
Police in Guangzhou could not be reached for comment.
A Taiwanese NGO worker who sought to promote democracy in China went missing after entering the mainland earlier this month, according to Taiwan authorities.
Lawyers, activists and academics in China are often accused of being in cahoots with foreign organisations trying to undermine national security and stir up opposition to the communist government. (AFP)