Australia slams China's 'unacceptable' treatment of jailed writer

Australia's foreign minister on Monday said the treatment of a writer detained in China was "unacceptable", after reports emerged of torture and daily interrogation.

In an unusually frank statement, Marise Payne said she was "very concerned by reports from a recent consular visit to Australian citizen Dr Yang Hengjun".

Yang has been detained in China since January and was recently charged with spying, which could bring a lengthy prison sentence.

Payne said Yang is subject to "increased isolation from the outside world, with restrictions on his communications with family and friends, and the resumption of daily interrogation, including while shackled".

"This is unacceptable," she said, adding 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 a string of foreign nationals recently arrested in China -- was a spy.

The arrests have been described by rights groups as politically motivated.

China's near-silence about Yang's fate has been a point of friction in relations with Australia.

Yang had initially been held in "residential surveillance at a designated location" before being moved to criminal detention in August.