Photo/Illutration This undated photo released by Chongyi Feng shows Yang Hengjun and his wife Yuan Xiaoliang. (Chongyi Feng via AP)

SYDNEY--A verdict in the espionage trial of Australian writer Yang Hengjun, detained by China since his arrest there four years ago, has been delayed until April, the seventh such delay, his supporters said on Thursday.

Pro-democracy blogger Yang is an Australian citizen born in China who was working in New York before his arrest at Guangzhou airport in 2019, coinciding with deteriorating relations between Australia and China.

A Beijing court heard Yang’s trial in secret in May 2021 and the case against him has never been publicly disclosed. Yang has denied working as a spy for Australia or the United States.

“The Australian government is deeply troubled by the ongoing delays in his case. Since Dr Yang was detained, the Australian government has called for basic standards of justice, procedural fairness and humane treatment to be afforded to Dr Yang,” Foreign Minister Penny Wong said in a statement marking the fourth anniversary of his detention.

Yang’s case, and that of detained Australian journalist Cheng Lei, tried in secret on national security charges in March 2022, are being closely watched in Australia as the two nations seek to improve diplomatic ties after a leaders meeting.

The first consular visit since October to the two journalists detained in Beijing took place on Jan. 13, after the Australian government called for consular access to be restored. Chinese authorities had previously suspended visits citing COVID-19 restrictions.

A verdict in Yang’s trial has been delayed by the court seven times, and his lawyer was told the deadline had been extended a further three months to April, his supporters told Reuters.

“Yang’s arbitrary detention in China is an outrageous political persecution due to his advocacy for universal values such as human rights, democracy and the rule of law,” said his former PhD supervisor at the University of Technology in Sydney, Feng Chongyi.

He urged the Australian government to secure Yang’s release before any resumption of normal trade with China, adding there were concerns over his health, including malnutrition, after four years of imprisonment.

China’s embassy in Canberra did not immediately respond to a request for comment.

The Chinese ambassador to Australia, Xiao Qian, told reporters in Canberra on Jan. 10 “there is nothing the government can do” in the two cases because they were before the courts.

“Once there’s a solution, there will be an announcement at the proper time,” he said.

In a message viewed by Reuters that Yang sent to his friends from prison this month, he maintained his innocence.

“Four years is a long time. I came, I suffered, I thought. But I have not been conquered,” Yang wrote in the message.