Mitsubishi Corp, Japan's biggest trading group, said on Wednesday it would shut its Singapore-based crude oil and fuel trading unit after revelations in September that a trader there racked up enormous unauthorised trading losses.

The unit, Petro-Diamond Singapore, will lose about 34.2 billion yen ($314 million) before taxes after closing the unofficial trading positions. That means the final debt for the unit could be as high as 30.8 billion yen, the company said in a statement.