Australian writer Yang Hengju

MELBOURNE/BEIJING: Chinese-Australian writer and political commentator Yang Hengjun , who was detained by China in January, has been formally arrested on suspicion of spying, Beijing confirmed on Tuesday.

The 54-year-old Yang had been under investigation for "harming" China's national security and was arrested on August 23 on suspicion of committing crimes of espionage.

Australian foreign affairs minister Marise Payne said the government efforts to gain additional information had been difficult.

"The government is very concerned and disappointed to learn that Australian citizen and academic Yang Hengjun was formally arrested in China on suspicion of espionage on 23 August and will continue to be criminally detained," she said.

"Our thoughts are with Dr Yang and his family at this very difficult time. Yang has been held in Beijing in harsh conditions without charge for more than seven months.

"Since that time, China has not explained the reasons for Dr Yang's detention, nor has it allowed him access to his lawyers or family visits," the minister was quoted as saying by the Australian Broadcasting Corporation (ABC).

She said consular staff had been approved for another visit to Yang on Tuesday.

"We have serious concerns for Dr Yang's welfare, and about the conditions under which he is being been held. We have expressed these in clear terms to the Chinese authorities," she said.

"I respectfully reiterate my previous requests that if Dr Yang is being held for his political beliefs, he should be released," she added.

In Beijing, China's foreign ministry on Tuesday said Yang is suspected of engaging in criminal activities that endanger the country's security.

Yang was formally arrested Friday by the Beijing branch of China's National Security Bureau on "suspicion of espionage," ministry spokesman Geng Shuang said.

"The Chinese state security organs handled the case according to law and fully guaranteed the various rights of Yang Jun. Yang Jun is currently in good health," Geng told reporters at a briefing.

He also expressed China's "strong dissatisfaction with Australia 's statement on the case."

"The Australian side should earnestly respect China's judicial sovereignty and must not intervene in China's handling of the case in any way," he asserted.

Under the Chinese law, the penalties for espionage charges range from three years in jail to the death penalty.

Yang had been living with his family in New York, where he was a visiting scholar at the Columbia University .

He flew to the southern Chinese city of Guangzhou with his wife and child in January this year.

Yang's family were allowed to board their connecting flight to Shanghai , but authorities escorted him from the airport, the ABC report said.

Yang is the latest in a string of foreign nationals to be arrested in China and charged with espionage. Two Canadians, former diplomat Michael Kovrig and businessman Michael Spavor, were detained in December.

China has denied the detention of the two men is linked to Canada's arrest of a senior Huawei official, Meng Wanzhou. Meng is the daughter of Chinese telecom giant Huawei founder Ren Zhengfei.

