China said Thursday that Chinese-Australian author and democracy advocate Yang Hengjun was detained on national security grounds, becoming the latest Western citizen to face such accusations from Beijing.

Yang's detention comes at a moment of heightened tension between Western countries and an increasingly muscular Beijing, which recently detained two Canadians amid a diplomatic row with Ottawa.

Australia demanded that Yang -- a former Chinese diplomat -- be treated "fairly and transparently" and complained that Beijing had waited four days, instead of three as required, to notify Canberra about his detention.

Yang was detained shortly after he made a rare return to China from the United States last week.

"Beijing state security took compulsory measures against Australian national Yang Jun and are investigating because he is suspected of engaging in criminal activities that endanger China’s national security," said Chinese foreign ministry spokeswoman Hua Chunying, using Yang's official name.

Such accusations in China often imply espionage allegations. Similar allegations were made against the two Canadians who were detained in December.

Australian Defence Minister Christopher Pyne, on an official visit to Beijing, told reporters he would be raising the issue with his Chinese counterpart later on Thursday.

"As Mr Yang doesn't have a residence in Beijing, I believe he would be held in a... situation which we would describe as home detention," he said.

Yang's lawyer Mo Shaoping confirmed to AFP that his client is under residential surveillance, adding that Yang Hengjun is his pen name.

But Yang may not have access to his lawyer anytime soon -- a visit will require approval from the Beijing State Security Bureau, standard procedure in such cases involving national security.

Australian Foreign Minister Marise Payne said earlier that diplomats met with Chinese officials in Beijing to discuss the matter and called on China to deal with the matter "transparently and fairly".

Once described as China's "most influential political blogger", Yang became an Australian citizen in 2000, but is currently based at New York's Columbia University.

His criticism of the Chinese government and support for democracy has in the past made him a target of Beijing's state security apparatus.

He went missing during a 2011 trip to China, but resurfaced days later, describing his disappearance as a "misunderstanding".

- Strained relations -

Canada's arrest on December 1 of a senior executive of Chinese telecom giant Huawei at Vancouver airport was followed days later by the high profile arrests in China of the two Canadians, former diplomat Michael Kovrig and businessman Michael Spavor.

Payne said there was "no evidence" Yang's arrest was part of that trend "at this stage", adding "I'd be concerned if there was an indication of that."

"It only heightens the feeling that visiting China is unsafe and that the security services may increasingly be going after people for what they say outside of China," said longtime China-watcher Bill Bishop.

Relations between China and Australia have likewise been strained by Canberra's decision to ban Huawei from participating in its 5G wireless network over security fears and as the two countries have vied more openly for influence in the Pacific.

Yang had worked in the ministry of foreign affairs in Hainan province, but later left for Hong Kong in 1992, before writing a series of politically tinged spy novels. He became an Australian in 2000.

Yang's friends first raised concerns when the 53-year-old failed to make a connecting flight from Guangzhou to Shanghai on January 19.

He was reportedly travelling with family members, including his wife, who has since posted a cryptic and emotional message on her Weibo page from Beijing.

In Australia there is mounting anger that China failed to quickly notify the authorities of his detention and fears that an already difficult relationship may be further damaged.

"This is not the way relations between our two countries should be conducted, at all," said Australian opposition leader Bill Shorten, criticising the slow response from the Chinese authorities.

Hua countered that Chinese authorities "officially notified the Australian side after taking mandatory measures" against Yang, but she did not say exactly when.

Under a 2000 consular agreement between the two countries, China was obliged to notify Australia of Yang's detention within three days and allow consular visits, unless the detainee waives that right.

The issue may be further complicated by China's refusal to recognise dual nationality and allegations of Chinese "hostage diplomacy".

Writers' advocacy group PEN accused China of overt repression, saying: "It's obvious that Yang would not have been seized if it weren't for his previous critical writings."