Cheng Lei is a prominent television anchor on the Chinese government's English-language network CGTN.

Friends and family have been unable to contact her for weeks.

The Australian government has confirmed she has been in custody since August 14.

Her family is seeking legal counsel as Australian consular staff offer assistance.

Geoff Raby, a former ambassador to China who runs a consultancy firm in Beijing, is a close friend of Cheng.

"Everyone in her circle is just astounded this has happened," he told ABC radio on Tuesday.

"Cheng Lei is a very skilful operator. She knows where the limits on public comment are in that sort of system. She understands how it works, she is pragmatic and hard-headed.

"It is very hard to see where the sensitivity is and where she may have overstepped any red lines around political sensitivities in China."

Mr Raby said Cheng did a slightly sardonic recent piece on coronavirus, but it was scarcely enough to rankle authorities in Beijing.

He described her as an objective and balanced journalist who would argue from China's corner in private conversations.

Mr Raby believes Cheng's detention is linked to diplomatic tensions between China and Australia.

"I would like to think otherwise, but it's very hard to think otherwise," he said.

"The timing is not accidental, that is for sure.

"Whatever else is behind this case, it is clearly part of what is happening now, a tit-for-tat down to an even lower level in the relationship."

Foreign Minister Marise Payne rejected speculation the prominent journalist was being used as a pawn.

"I would not describe it in that way - it is speculative at best to engage in that sort of premise," she told 2GB radio.

Senator Payne said Cheng was doing "as well as can be expected" under the circumstances.

China relations have been heavily strained after Australia led calls for an independent inquiry into the origins of coronavirus.

Beijing has since launched trade strikes on Australian beef, barley and wine.

Asked about whether China was engaging in coercive diplomacy, Trade Minister Simon Birmingham responded by citing an Australian Strategic Policy Institute report, which found exactly that.

Cheng is not the only Australian detained in Beijing.

Australian writer Yang Hengjun has been detained since January 2019 and could face the death penalty if found guilty of espionage.

Cheng's family has issued a statement saying they respect China's legal processes, and urging people to limit comments on her case.

Born in China, Cheng studied commerce at the University of Queensland before working for Cadbury Schweppes and ExxonMobil in Australia.

In an online video for the Australia Global Alumni posted two years ago, Cheng praised the value of her Australian education.

"The beauty of an Australian education is not about what is taught but more about what it doesn't teach," she said.

"It doesn't teach you to just follow orders, it allows you the freedom to think for yourself, to question ... to judge for yourself."

After moving to China, Cheng - who speaks with a distinct Australian accent - worked for the Chinese state broadcaster, the country's biggest TV network.

Under Chinese law, she could be held for months without charge.

Australian Associated Press