The four, including Stern Hu, Rio Tinto's general manager in Shanghai, were accused of stealing China's state secrets, China's state-run Xinhua news agency reported.
"Hu is suspected of stealing China's state secret. The four people including Hu had been detained by China's security authorities Sunday evening," Chinese Foreign Ministry spokesman Qin Gang told reporters Thursday in Beijing.
Hu is an Australian citizen of Chinese origin, and is a longstanding employee of Rio Tinto, Australian Foreign Minister Stephen Smith was quoted as saying. Hu and his wife, also an Australian citizen, reportedly have lived in Shanghai for a number of years.
The other three accused were holding Chinese passports, Xinhua reported.
"China will handle the case properly according to law," Qin said. "This is an individual case and should not be exaggerated or even politicized."
A statement e-mailed from Rio Tinto to Xinhua Thursday was quoted as saying: "We have been advised by the Australian government of this surprising allegation. We are not aware of any evidence that would support such an investigation."
The company also was quoted as saying it would cooperate fully with any investigation the Chinese authorities may wish to undertake and has sought clarification on what has occurred.
A month ago, Rio Tinto, the world's second largest mining company, backed away from a $19.5 billion deal with Chinalco, a Chinese state-owned company, but Australian officials have said the spy allegations did not appear related to company business.