CANBERRA, Australia - Australia has asked China for information on a Chinese-born Australian writer who disappeared in the country, the government said Tuesday amid reports he may have been detained in Beijing's ongoing crackdown on political expression.

Sydney-based spy novelist Yang Hengjun phoned a friend Sunday from Guangzhou airport in southeastern China to say three men were following him, the Sydney Morning Herald newspaper reported. He has not been heard from since.

Australia's Department of Foreign Affairs confirmed Tuesday that it is investigating the disappearance.

Yang, 46, was an official in the Chinese Foreign Ministry before moving to Australia. His novel, "Fatal Weakness," deals with espionage between China and the United States and has been published on the Internet in China.

He also writes a blog that frequently discusses issues involving China's government, according to Feng Chongyi, Associate Professor in China Studies at the University of Technology in Sydney.

Yang is "the most influential political blogger in China, with millions of readers," Feng told the Sydney Morning Herald.

China's authoritarian government has in recent weeks harassed and detained dozens of activists to prevent any copying of the democracy uprisings across the Middle East.

China's Foreign Ministry said it had no information on Yang.

"I have not heard of that person," spokeswoman Jiang Yu told a regular news conference in Beijing on Tuesday.