Australia has abruptly revoked the visas of two visiting Chinese scholars as part of wider probe into illegal Chinese activities considered threats to Australian national security.

The Australian Department of Home Affairs (DHA) sent email letters to Chen Hong, a professor of Australian Studies at East China Normal University in Shanghai, and Li Jianjun, an Australian studies scholar at the Beijing Foreign Studies University, announcing the revocation of their visas.

DHA told both academics their Australian visas were being cancelled on the advice of the Australian Security Intelligence Organization (ASIO), which said they represent risks to national security. ASIO is comparable to the U.S. Federal Bureau of Investigation.

Chen and Li are the heads of Australian studies centers at Shanghai's East China Normal University and the Beijing Foreign Studies University. Li is also studying for a PhD at Western Sydney University. His student visa was previously revoked. Chen, a frequent visitor to Australia, has published stories in Australian media and the Global Times, a tabloid owned by the Communist Party of China (CPC).

Both academics had their visas revoked as part of an ongoing investigation by ASIO and the Australian Federal Police (AFP) into an alleged plot by the CPC to infiltrate the New South Wales Parliament by using the office of Labor Party backbencher Shaoquett Moselmane. John Zhang, a former staffer of Moselmane's, was accused of trying to influence the lawmaker into doing China's bidding.

Also being investigated by the AFP-ASIO Foreign Interference Task Force along with Chen and Li are Tao Shelan, Australia bureau chief of China News Service, and Li Dayong, Sydney bureau chief of China Radio International.

The task force alleges Zhang used a chat group on WeChat, the popular Chinese social media platform, to goad Moselmane into advocating Chinese government interests.

In June, the AFP-ASIO task force raided the homes and offices of Moselmane and Zhang, seizing devices and files. Beijing continues to retaliate for this raid, and this week forced the hasty departure from China of ABC correspondent Bill Birtles and Australian Financial Review journalist Michael Smith .

It had previously ordered the arrest of another Australian, TV news anchor Cheng Lei. She was detained in August and is accused of being a threat to China's national security.

In a statement, Chen said he was shocked to receive an email notifying him of the visa cancellation on security grounds.

"I absolutely refuse to accept this assessment, and believe a gross mistake has been made regarding my relationship with Australia," he said. "I have done nothing and will do nothing to act as a risk to Australia's security."

Chen, a friend of both Zhang and Moselmane, told ABC News Australia the WeChat group, "FD group" or "Fair Dinkum group," allegedly used in the plot against NSW was just an innocuous forum.

"The group was a most ordinary social network platform on which members used to share jokes and funny memes, photos of personal excursions, fishing trips or drinks, and repost newspaper articles," he wrote.

"The allegation that the group had been purported as a means of influence is simply preposterous. Everything about the group is open to scrutiny."