Australian journalist Cheng Lei was due to face trial in a heavily-guarded Beijing court on Thursday on state secrets charges after more than 19 months in detention.
Cheng, who was a television anchor for Chinese state broadcaster CGTN before being detained in August 2020, was formally arrested a year ago on suspicion of illegally supplying state secrets overseas.
Cheng's family members have said they are convinced she is innocent.
Outside the No.2 People's Intermediate Court where Cheng was to be tried on Thursday morning, a heavy security presence included uniformed police and plain-clothed security personnel. Police, who had taped off areas close to the north entrance of the court, checked journalists’ IDs and asked them to move away.
Australian Ambassador Graham Fletcher was barred from entering the court.
"This is deeply concerning, unsatisfactory and regrettable. We can have no confidence in the validity of a process which is conducted in secret," he told journalists before leaving.
A court official told Fletcher that he could not be admitted because the case involves “state secrets” so the trial cannot be public.
Australian Foreign Minister Marise Payne said in a statement on Saturday that her ministry had asked Chinese officials that Australian officials be allowed to attend Cheng's hearing in line with a consular agreement between the two nations.
"We expect basic standards of justice, procedural fairness and humane treatment to be met, in accordance with international norms," she said.
Payne said Australian officials have had regular visits with Cheng, most recently on March 21.
Australia has previously said it was concerned about Cheng's welfare and conditions of detention and what it said was a "lack of transparency" over the case.
China's courts have a conviction rate of well over 99%, according to calculations by China Justice Observer, a local web portal.
"Her two children and elderly parents miss her immensely and sincerely hope to reunite with her as soon as possible," Cheng's family said in a statement provided to Reuters.
At a news conference earlier this week, a Chinese foreign ministry spokesman did not directly respond to a Reuters query on whether Australian officials would be permitted to attend, but did say that Cheng's rights would be fully guaranteed.
Last May, in a separate case at the same court, Australia's ambassador to China was denied entry to the trial of Australian blogger Yang Hengjun, who was accused of espionage. In a trial last March of Canadian former diplomat Michael Kovrig in the same court, Canadian officials were denied entry.
Cheng was born in China and moved with her parents to Australia as a child. Later she returned to China where she built a television career first with CNBC, starting in 2003, and later, starting from 2012, as a prominent business news anchor for China's English-language CGTN.
The trial comes as diplomatic relations between Australia and China remain tense, after Canberra urged an international probe into the source of the COVID-19 pandemic in 2020 and Beijing responded with trade reprisals.
(Reporting by Martin Quin Pollard in Beijing and Kirsty Needham in Sydney; Editing by Tony Munroe, Raju Gopalakrishnan & Shri Navaratnam)