The "Rio Tinto four" will now go on trial in a case that has become a symbol of growing concern for foreign corporations in China. The mining giant has repeatedly denied the allegations against its employees.

The four employees have been held in China since July 2009, including Stern Hu, an Australian national. Although the serious charge of stealing state secrets has been reduced, they still face over 20 years in prison if convicted.

The indictment by Shanghai prosecutors alleges that the mining salesmen accepted bribes from several Chinese steel enterprises. It also says they used improper means to obtain commercial secrets that caused serious consequences for other companies.

The case has sparked fear among international businessmen working in China because of a lack of transparency on corruption and espionage rules.

The dispute has increased China's tension with Australia, with Beijing claiming that Rio Tinto inflated the price of iron ore in the country.