BEIJING (AP) — The Australian ambassador to China said it was “regrettable” that the embassy was denied access Thursday as a trial was due to start for a Chinese Australian man charged with espionage.

Yang Hengjun has been held since arriving in China in January 2019 and has had no access to family and only limited contact with his lawyer, the Australian government has said.

Ambassador Graham Fletcher walked to the south gate of the court complex in Beijing and then came back out after he had been denied access. His government had been told earlier that a representative would not be allowed to attend the trial because it is a national security case.

“This is deeply regrettable and concerning and unsatisfactory,” he told reporters. ‘"We’ve had longstanding concerns about this case including lack of transparency and therefore have concluded that it's an arbitrary detention."

Authorities have not released any details of the charges against Yang.

The trial comes at a time of deteriorating relations between the two countries. China has blocked Australian exports including beef, wine, coal, lobsters, wood and barley. However, Australia’s most lucrative export, iron ore, still has eager buyers among Chinese steel manufacturers.

A close family friend, Feng Chongyi, recently described the case against Yang as “fabricated ... for political persecution and political purposes and I have never had any illusion for a fair trial."

“Given Beijing’s determination to punish him and the current bad relations between Australia and China, I am deeply concerned that Yang’s sentence will be harsh," Feng said.