According to news reports out of China, the four Rio iron ore executives being detained in Shanghai, including Australian Stern Hu, have been formally charged with espionage.

Chinese news sources say the government yesterday claimed there is “sufficient evidence” that the Rio executives have committed espionage and revealed state secrets, causing a “huge loss” to China’s economic interests.

There have also been reports of a wider investigation into the Chinese steel industry, with a senior executive from steel mill Shougang – and a friend of Stern Hu – also said to have been arrested.

Opposition Leader Malcolm Turnbull said that Prime Minister Kevin Rudd and the Labor government had not done enough to support Hu, and insisted Rudd contact Chinese president Hu Jintao personally to call for the release of the Australian executive.

Rudd has denied the claims and said his government was doing everything it could to support Hu, and was also in regular contact with Rio Tinto.

Australian officials will have access to Hu today.

The Australian government earlier this week said it had no knowledge that Hu’s arrest had a direct link to the fraught iron ore pricing process, still ongoing between Chinese steel mills and the major iron ore miners, including Rio Tinto.

However, Chinese news agencies suggest it is precisely information about iron ore pricing that is behind the arrest of Hu and the other Rio executives.

The federal government has also rejected claims the detaining of the executives has anything to do with Rio’s actions last month, when it ditched Chinese company Chinalco as a major investor and partner in favour of a tie-up with major miner BHP Billiton.