Yang Hengjun and his wife Xiaoliang Yuan. Yang, an Australian citizen, was detained by Chinese intelligence officials when he flew from the US to Guangzhou on January 19.

Two Australian writers, including one now detained in China, were the targets of a Chinese government intelligence operation conducted partly on Australian soil.

An investigation by The Age, The Sydney Morning Herald and Four Corners can reveal that the Chinese operation was seeking details about former prime minister Malcolm Turnbull's 2016 classified inquiry into Beijing's campaign to influence Australian politics.

Blogger Yang Hengjun, who is currently detained in China, and Sydney academic-writer, Dr Feng Chongyi, were both targeted by Chinese authorities for information on John Garnaut, the China expert and former journalist who led the classified investigation.

The revelations come as Yang's wife Xiaoliang Yuan broke her silence from China – risking potential blowback from the Chinese government – to call for Australia to fight harder for her husband's release from the "residential detention" facility he's been held in since travelling there in January.

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Liberal MP Andrew Hastie has joined Yang's wife to issue an impassioned plea for Australians to demand his release from Beijing detention.

While some details of Yang's detention by Chinese intelligence officials in Beijing have filtered to the outside world, his questioning by Chinese agents in Sydney in March last year has never been made public.

Yang was allegedly intercepted and questioned just prior to a meeting with Garnaut.

PETER RAE/FAIRFAX AUSTRALIA Former journalist John Garnaut was handpicked by Malcolm Turnbull in 2016 to help the ASIO assess Chinese government interference in Australia.

​Garnaut has revealed that Yang told him Chinese officials had questioned Yang "about me, what was the nature of our relationship, what was I doing, what was I working on".

Garnaut – an award-winning former China correspondent with The Age and SMH who was handpicked by Turnbull in 2016 to work with the Australian Security Intelligence Organisation (ASIO) to assess Chinese government interference in Australia – had developed a friendship with Yang after meeting him as a journalist in 2008.

Garnaut's classified work for Australia's federal government, which he refuses to talk about and which has never been disclosed in any detail, appears to have prompted Chinese intelligence officials to also grill Dr Feng when they detained him for six days in China in 2017.

Feng has revealed that the intelligence officials interrogating him wanted to know "in every detail" what Garnaut was doing on behalf of Turnbull and the government.

"They knew a lot about him. During the interrogation, they did not hide that they were angry with him," Feng said.

Garnaut, said the questioning of Feng while Garnaut was working for the Australian government "seems to add an extra layer of contempt" by Beijing for Australian sovereignty.

TREVOR COLLENS/FAIRFAX AUSTRALIA Liberal MP Andrew Hastie has issued an impassioned plea for Australians to demand Yang Hengjun's release from Beijing detention.

Australian and US government sources have confirmed the Turnbull-commissioned Garnaut-ASIO report, finished in mid-2017 and never released, uncovered damning new evidence of interference and influence involving Chinese government officials and, separately, Communist Party-aligned businessmen seeking political favours and access.

Investigations over several years by The Age and SMH with Four Corners have revealed the most compelling evidence ever made public about Beijing's interference.

Hastie, who chaired the parliamentary committee on intelligence and security that pushed through new counter-interference reforms in 2018, has made the most strident comments about Beijing to emerge from the current Australian government.

"We've had multiple briefings at the top-secret level from ASIO and other agencies that foreign interference is being conducted in Australia at an unprecedented level," Hastie said.

"There are several authoritarian states who are involved in foreign influence across the globe. But in Australia the Chinese Communist Party is probably the most active … China is seeking to influence our elites, particularly our political and business elites, in order to achieve their strategic objectives."

STEVEN SIEWERT/FAIRFAX AUSTRALIA Dr Feng Chongy says Chinese intelligence officials interrogating him wanted to know "in every detail" what Garnaut was doing on behalf of the Australian government.

Hastie has said all Australians should fight for Yang's release.

"Mr Yang is an Australian citizen. He enjoys the rights and responsibilities of Australian citizenship. And so his detention, in a sense, is a detention of us all. We're all Australian citizens. How could we guarantee that we wouldn't be detained if we went to China?"

Yang's wife, Xiaoliang Yuan, has also broken her silence in Shanghai to urge the Australian government to increase its efforts to release her husband, who became an Australian citizen in the early 2000s.

"I think at least, the Australian government officials should care for its citizens' wellbeing when they are overseas, should show their concern. But I now feel like, to be honest, I have been very disappointed," she said.

Yang was detained by Chinese intelligence officials when he flew from the US to Guangzhou on January 19 and has been accused of endangering state security. Yuan said she had been advised by the Australian consulate she will be granted permanent residency in Australia, but said she had been banned by local authorities from leaving China.

"It gets harder as time passes. You just can't see him. I would have felt better if the lawyers could see him and verify that he is all right. There is absolutely nothing we can do at the moment.

"I just want him to come home safely," she said, in tears.

Garnaut has joined calls for more action from the government behind closed doors and in public.

Xiaoliang Yuan says she just wants her husband home safely.

"I'd like to, at the very least, see some really strong statements about what this is, and why Yang is important to the Australian community, the Australian society," Garnaut said.

Garnaut now works for McGrathNicol, a firm which advises companies on Chinese government risk.

Australia's Attorney-General Christian Porter said providing consular assistance to Yang had "proved somewhat difficult" but that officials were doing all they could to assist the detained Australian.

Yuan has taken a risk in speaking out publicly while she is still based in China, given the sensitivity around her husband's detention. She said she was prompted by Australia's lack of action.

Feng has also taken a risk in speaking out about his interrogation in China. In his final interrogation session, Chinese security officials warned Feng that if he disclosed the details of his interrogation – including their interest in Garnaut – he would face criminal charges if he ever returned to China.