Yang Hengjun, a former Chinese diplomat turned online journalist, has been held in China since January.

Australia’s foreign minister Marise Payne said on Monday said the treatment of an Australian writer detained in China was “unacceptable”, and called for more details on his case in a move likely to increase tensions with the government in Beijing.

Yang Hengjun, a former Chinese diplomat turned online journalist and blogger, was formally arrested in August on suspicion of espionage, seven months after he was first detained in the southern city of Guangzhou.

In an unusually frank statement, Payne said she was “very concerned” by reports she had received from Australian embassy officials who recently visited Yang in detention.

“His circumstances of detention include increased isolation from the outside world, with restrictions on his communications with family and friends, and the resumption of daily interrogation, including while shackled,” Payne said in an emailed statement.

“This is unacceptable.”

Payne said Australia has asked for an explanation of the charges against Yang, and that repeated requests had been made for Yang to get “basic standards of justice, procedural fairness and humane treatment”.

Prime Minister Scott Morrison has denied that Yang – one of several of foreign nationals recently arrested in China – was a spy.

Morrison said the welfare of an Australian citizen was paramount, and that the authorities had been raising concerns about Yang’s imprisonment “for some time.”

“Australia always has to stand up for our citizens and we have to be true to who we are as a people,” Morrison told reporters in Canberra.

Rights groups worry whether those detained will be tried fairly, and say governments need to increase international pressure on China.

“The worrying part is how the so-called trial will happen, and if it does happen at all how it will be conducted,” Amnesty International’s China researcher Patrick Poon told Al Jazeera from Hong Kong. “Unfortunately, from previous experience in other cases it is very unlikely he will be given a fair trial.”

Health concerns

Yang was initially held in “residential surveillance at a designated location” before being moved to criminal detention in August.

Although Yang’s more recent writings had mostly avoided Chinese politics, he became prominent in the early 2000s when he was nicknamed “democracy peddler”.

Morrison said Australia wanted to see clear details of the case against Yang, and to ensure that he had access to his lawyers and family members.

One of Yang’s Australian lawyers, Sarah Condon, said China’s Ministry of State Security was giving 54-year-old Yang several medications daily because they had diagnosed high blood pressure and kidney function issues.

“We’re concerned because he went in as a fit and healthy man,” Condon told Reuters. “Now he has this purported diagnosis and is being fed a concoction of drugs.”

Australia’s prime minister on Monday announced the government would spend A$87.8 million ($59.58 million) to create a new taskforce to tackle foreign interference.

Morrison did not specifically mention China, but Canberra has become increasingly wary about Beijing’s influence within Australia and across the Pacific.

Earlier this year, Reuters reported Canberra had determined that Beijing was responsible for a cyber-attack on Australia’s parliament and the country’s three largest political parties.

China denied it was behind the attack. It last month refused two Australian lawmakers visas to enter China.

China buys more than a third of Australia’s total exports and the country is a popular destination for Chinese tourists and students.