The three-day trial of four Rio Tinto executives concluded on Wednesday without a verdict, a lawyer said.

The trial wrapped up at Shanghai No 1 Intermediate People's Court at midday, and no date was set for the verdict, said Zhai Jian, an attorney representing one of the accused.

The four, including Australian national Stern Hu and his three Chinese colleagues - Liu Caikui, Ge Minqiang and Wang Yong - were charged with taking bribes of more than 86 million yuan (US$12.6 million) and stealing commercial secrets.

All four pleaded guilty to bribery charges on the first day of the trial although they disputed the specifics of the charges.

The guilty plea came as a surprise to many as Rio Tinto had earlier defended the innocence of its four employees, claiming that they "had done nothing wrong".

Court proceedings dealing with the theft of commercial secrets were held behind closed doors on the second and third day, and few details were made public.

Media reports cited another lawyer, Zhang Peihong, as saying three of the four defendants on trial for stealing commercial secrets had contested the charge.

The indictment alleges the four used improper means to obtain commercial secrets from Chinese steelmakers. The information they obtained is believed to have been used as a bargaining chip to drive up the price that China pays for its iron ore imports.

In a statement, the spokesperson for the Australian Department of Foreign Affairs and Trade said "they were not in a position to say anything further at this point", but that Australian consular officers "will be present when the court reconvenes to announce its verdict".

The statement also said the court will deliver its verdict "at a date to be determined".

"The Australian government will continue to provide consular assistance to Mr Hu throughout this process, consistently engaging the Chinese authorities to safeguard his welfare and rights under Chinese law. We continue to maintain close consultation with Hu's family and his employer," it said.

The four face jail terms of at least five years for bribery, and the maximum penalty for industrial espionage is seven years.