Anglo-Australian mine giant Rio Tinto has signed a deal with Chinese state company Chinalco to build a huge mine in the West African country Guinea.

The deal is worth almost a billion euros. The agreement comes three days before the trial in China of four top Rio Tinto employees for bribery and industrial espionage.

One of the four has an Australian passport, the other three are Chinese. Their arrests raised tensions between Canberra and Beijing. Australian Minister Simon Crean says the African project is a completely separate matter to the trial.

Rio Tinto and Chinalco will build a mine in Guinea which will produce 200 million tonnes of iron ore per year in the future.

The project is controversial because of the political situation in Guinea. Last year, 150 people were killed in a bloodbath when the Guinean junta clamped down on demonstrators against the regime.