aSYDNEY: Australia on Saturday made high-level representations in China over the arrest of a top mining executive on bribery claims, as diplomatic tensions deepened between the key trading partners.

Trade Minister Simon Crean, who is in China on a pre-arranged diplomatic visit, contacted the Shanghai government to intervene on behalf of Rio Tinto's Stern Hu, who is accused of spying and stealing state secrets.

Beijing claims Hu, the head of Rio's Shanghai office, bribed staff at Chinese steel companies during protracted iron ore price negotiations, allegations which have "surprised and concerned" Rio.

Crean said he expressed "strong concern" to the city's deputy secretary general and urged expeditious treatment of Hu's case.

"We have reinforced in the strongest possible terms the importance of the matter being dealt with as expeditiously as possible, having regard to the processes of Chinese law," Crean told reporters in Shanghai.

"We respect the Chinese legal system and the processes that need to be gone through, but we've indicated this too is an important issue back home in Australia for us.

"We have conveyed the importance of this issue at the level of government here and we have been assured that that message will be conveyed."

Australian consular officials were late Friday granted access to Hu for the first time since his arrest without charge last Sunday, and said he seemed well.

"He appeared in good health and he said he was in good health," Crean said.

"We have conveyed that information to his family and of course we continue to follow with great concern the welfare of Mr Hu," he added.

Former Rio suitor, China's state-owned Chinalco, has denied Hu's arrest was payback for the collapse of its 19.5-billion-US-dollar takeover bid.

Rio, the world's third-largest miner, has been locked in difficult talks with China to set iron ore prices for the coming year, with negotiators missing a key deadline on June 30.

Rio iron ore chief Sam Walsh welcomed news of the consular visit, and said the company remained in the dark about the allegations.

"Rio Tinto continues to work to support its four China employees and their families and colleagues," Walsh said.

Rio remained surprised and concerned over the detention of Hu and three of his colleagues, Walsh said, adding that the company "had not been told by Chinese authorities of any charges against them".

Meanwhile, pressure mounted on Mandarin-speaking Prime Minister Kevin Rudd, who has come under fire for refusing to personally intervene in the case.

China is the world's biggest consumer of iron ore and Australia's second-most important trade partner, with the relationship worth 58 billion US dollars last year, according to official figures.

Nationals Senator Barnaby Joyce accused Rudd of giving China special treatment and said the arrest was a "set-up" by Beijing.

"We are being politically correct in how we are approaching this in a manner that we wouldn't be if this person were detained in the United States, Japan or India, or New Zealand or Canada," Joyce said.

"It gives more credence to the argument that this is a political set-up by China, retribution for the actions of Rio or what they believe is a deal that hasn't gone their way," he added.

Hu's former boss, John Dougall, who sponsored his bid to become an Australian citizen in 1994, accused Canberra of abandoning him, and called for greater diplomatic pressure.

"Mr Rudd has to do more than sit back and let Stern be thrown to the wolves," Dougall told Sky News.

"Many people in Australia and China regard Stern as a trade hero and his treatment is outrageous."

Greens Senator Bob Brown and opposition leader Malcolm Turnbull also urged Rudd to intervene.

"Prime Minister Rudd should've been talking at heads-of-government level because we're dealing with a government in China which effectively runs the judicial system," Brown said.