Xi Jinping and Scott Morrison (Images: AAP)

Australia's business engagement with China -- for decades the object of encouragement and enthusiasm by successive governments eager to take advantage of a massive economic opportunity -- is now a potential source of vulnerability after three Australian journalists were targeted.

After facilitating the flight of journalists Bill Birtles and Michael Smith in the face of pressure from Chinese police -- ostensibly related to the arrest and detention of Australian-Chinese TV anchor Cheng Lei -- the Department of Foreign Affairs confirmed its advice that Australians should not travel there given "authorities have detained foreigners because they're 'endangering national security'. Australians may also be at risk of arbitrary detention."

The advice is slightly more guarded for Australians already there: "If you’re already in China and wish to return to Australia, we recommend you do so as soon as possible by commercial means."