A high-profile Australian journalist who worked for Chinese official media and was missing for weeks is being held on charges of endangering “national security”, China said on Tuesday.

Cheng Lei, who worked as an anchor for China Global Television Network (CGTN) channel, is suspected of “criminal activity of endangering China’s national security”, the Chinese foreign ministry announced.

The channel is the only English channel of national broadcaster, China Central Television.

Authorities had taken “compulsory measures” against Cheng, foreign ministry spokesperson, Zhao Lijian said at the regular ministry briefing on Tuesday.

Cheng, a Chinese-born Australian anchor, was detained on August 14, the Australian foreign ministry had said last month.

Australian diplomats spoke to her from her detention facility over video at the end of August.

Zhao didn’t share details of the charges levelled against Cheng.

Zhao’ announcement came hours after the last two Australian journalists flew back to Sydney in late night flights after a five-day diplomatic stand-off.

The Australian Broadcasting Corporation’s (ABC) Bill Birtles in Beijing and the Australian Financial Review’s (AFR) Mike Smith in Shanghai were apparently questioned in connection with Cheng’s case.

Birtles took refuge at the Australian embassy in Beijing and Smith at the country’s consulate in Shanghai after they were questioned by the police. They left China after diplomatic negotiations gave them a window to leave China.

With their departure, it will be for the first time that Australia will not have an accredited journalist in China since the 1970s.

In a statement, the Foreign Correspondents’ Club of China strongly condemned the Chinese government’s “…unprecedented harassment and intimidation of two Australian journalists by preventing them from leaving the country, leading both to flee China after a diplomatic standoff ended in a lifting of the bans.”

Calling it “appalling intimidatory tactics”, the FCCC said that such actions threaten and seek to curtain the work of foreign journalists based in China who now face the threat of arbitrary detention.

“This, combined with the expulsions of 17 foreign correspondents in the first half of this year alone, is a disappointing loss for global audiences seeking to understand more about China,” the FCCC statement added.