'Australian Held Over National Security Threats'

Beijing said on 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 – a novelist, democracy advocate and former Chinese diplomat – was detained shortly after he made a rare return to China from the United States last week.

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

She also referred to allegations that China did not inform Australia about the arrest as per a pact signed by the two countries.

Hua said that authorities "officially notified the Australian side after taking mandatory measures" against Yang. She identified him as Yang Jun and it was not immediately clear whether that was his real name.

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.

Australian Defence Minister Christopher Pyne, on an official visit to Beijing, said Beijing took four days to notify Canberra.

He told reporters he would be raising the issue with his Chinese counterpart.

"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.

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

Yang had worked in the ministry of foreign affairs in Hainan province, but shifted to Hong Kong in 1992, before writing a series of politically tinged spy novels. He became an Australian in 2000. (AFP)