A Chinese-Australian writer who went missing at the weekend has been detained in China, the Australian government says.
Yang Hengjun, a former Chinese diplomat, has been held since flying from New York to Guangzhou on Saturday.
China informed Australia the 53-year-old popular blogger was in custody, but has not clarified why.
Australian Foreign Minister Marise Payne urged China to handle the matter "transparently and fairly".
Ms Payne said Australian embassy officials would meet with Chinese counterparts on Thursday to "arrange consular access at the earliest possible opportunity".
Mr Yang, an Australian citizen, travelled to China with his wife, Chinese national Yuan Rui Juan, and young stepson.
It is believed that Ms Yuan has been interviewed by Chinese officials in Beijing, after first travelling to Shanghai to leave her son with relatives.
Chinese officials have not commented since confirming Mr Yang's detention to Australia. On Wednesday, a foreign ministry spokeswoman said she was "not aware" of the case.
Mr Yang has a sizeable following online and has sometimes written critically about China's Communist Party, but less so in recent times. He also authors spy novels.
Mr Yang was briefly unreachable on a trip to China in 2011 - prompting fears he was missing - but later attributed the episode to a "misunderstanding".
He currently lives in New York and is a visiting scholar at Columbia University, said his friend Feng Chongyi, an academic at University of Technology Sydney.
Associate Professor Feng said he had warned Mr Yang recently against travelling to China, but Mr Yang replied that he considered himself to be safe.
Mr Yang had not responded to messages in recent days, his friend said.
"He is one of the most influential bloggers on political issues in China, where he's earned the nickname of 'Democracy Peddler' through talking about democracy and human rights," Associate Professor Feng told the BBC on Wednesday.
Correspondents say Mr Yang's case follows a similar pattern to the cases of the two Canadian citizens, Michael Kovrig and Michael Spavor, who were detained in China in recent weeks.
In both cases, the foreign ministry initially said it had no knowledge of them being held, then a few days later confirmed they were in the hands of state security.
Australia has previously expressed "concern" about the arrests of the Canadians.
China has denied the detention of the two men is tied to Canada's arrest of a senior Huawei official, Meng Wanzhou, but many analysts believe it is a tit-for-tat action.
Mr Yang's detention comes as Australian Defence Minister Christopher Pyne is due to visit Beijing on Thursday.