"China and Australia are important trading partners for each other," Qin said.

"We attach great importance to the stable development of economic and trade relations, but we are firmly opposed to anyone stirring up the case and interfering with China's independent judicial authorities."

Four Rio Tinto employees, including Stern Hu, a Shanghai-based Australian citizen, in charge of the company's Chinese iron ore business, were detained on July 5 while Rio Tinto was acting as lead negotiator for global iron ore suppliers in price talks with Chinese steel mills.

According to Chinese state media, the four were accused of bribing employees of Chinese steel companies to obtain confidential information on China's negotiating strategy.

Officials meet

Despite the warnings from Beijing, Australian government officials are continuing to press China for more details about the case.

Stephen Smith, the foreign minister, met He Yafei, the Chinese vice foreign minister on the sidelines of the Non-Aligned Movement summit in the Egyptian Red Sea resort of Sharm el-Sheikh on Thursday.

The meeting was the most senior yet between officials from Canberra and Beijing since the arrest of the four Rio employees.

Chinese officials declined to comment on the details of the talks, which came amid reports that Anglo-Australian owned Rio Tinto had pulled out its remaining research staff from China.

The mining company has made no official comment on the reports.

The incident has strained relations between Australia and one of its largest trading partners, with Rio Tinto playing a key role as a major supplier of iron ore and other raw materials to China's growing economy.

The Chinese government considers information about steel production, sales and iron ore costs to be secret, according to state media.

Chinese news reports have said that executives of at least five major Chinese steel producers and the industry association are also under investigation.

China's booming steel industry consumes up to 60 per cent of global iron ore production and Beijing is pressing for deep price cuts after two years of increases totalling more than 120 per cent.