(Bloomberg) -- China has formally arrested an Australian citizen who was formerly a news anchor for Chinese state television, escalating a case that has contributed to tensions between Beijing and Canberra.

Cheng Lei, a Chinese-born Australian who most recently worked for state broadcaster CGTN, was formally arrested in China on Feb. 5 following six months of detention, the office of Australian Foreign Minister Marise Payne said in a statement on Monday. Chinese authorities have advised that Cheng was “arrested on suspicion of illegally supplying state secrets overseas,” the statement said.

China had said in September that Cheng was “suspected of carrying out criminal activities endangering China’s national security,” among the most serious allegations ever brought against a foreign journalist based in the country.

She was detained in mid-August under a provision that allowed her to be held for as many as six months without charge or access to a lawyer.

Australian embassy officials have visited Cheng six times since her detention -- most recently on Jan. 27 -- in accordance with a bilateral consular agreement with China, the statement said.

Australia “has raised its serious concerns about Ms. Cheng’s detention regularly at senior levels, including about her welfare and conditions of detention,” the statement said. “We expect basic standards of justice, procedural fairness and humane treatment to be met, in accordance with international norms.”

Rising Tensions

The case came to light amid deteriorating relations between China and Australia, sparking fears that Beijing had targeted Cheng to exert pressure on Canberra. Tensions worsened after Prime Minister Scott Morrison’s government called for an independent probe into the origins of the coronavirus in April, a move seen in China as backing U.S. President Donald Trump’s efforts to blame it for the pandemic.

Chinese President Xi Jinping’s government placed tariffs on Australian barley, banned products from a number of meatworks and launched an anti-dumping probe into its wine exports. Still, China remains Australia’s largest trading partner, driven by the nation’s appetite for resources like iron ore and coal.

Cheng has hosted business shows as a CGTN anchor since 2012 and was well known among Beijing’s small circle of diplomats and journalists. She had previously served as China correspondent for CNBC, after graduating from the University of Queensland with a bachelor’s degree in commerce and serving a stint as an accountant at Cadbury Schweppes, according to her LinkedIn profile.

Cheng’s detention also coincided with a specific dispute between Australia and China over efforts by each other’s spy agencies to question foreign journalists. China withdrew four state media journalists from Australia after authorities raided their homes, while two Australian correspondents left China after state security agents sought them for questioning.

One of the Australian journalists, Mike Smith of the Australian Financial Review, said in September that Chinese officials asked him about Cheng, among other things, before he was allowed to leave. Chinese Foreign Ministry spokesman Zhao Lijian said separately that the cases of the Australian journalists and Cheng were unrelated to the raids on the Chinese journalists’ homes.

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