Japanese trading house Mitsubishi Corp said that its net profit for the six months ended September 30 fell 8.3% from a year earlier, citing lower margins from trading in natural resources and steel.

Mitsubishi, Japan's biggest trading house by revenue, also said it has decided to invest AUD 2.1 billion in a coking coal mine expansion project in Queensland, Australia, as it seeks new revenue sources in resource-related activities overseas.

Mitsubishi said the investment will expand the BHP Billiton Mitsubishi Alliance a joint venture between its wholly owned unit in Australia and BHP Billiton Ltd that operates mines in the coal rich Bowen Basin of Central Queensland.

The project will include development of the Caval Ridge mine and expansion of the Peak Downs mine located in the northern Bowen Basin.

The Tokyo based company said it generated a group net profit of JPY 245.69 billion in the first half of the fiscal year, compared with JPY 267.96 billion in profit in the same period in the previous year.

The company cited a decline in sales volume at its natural resources unit in Australia and low trading volume at its steel product unit. The company also cited a high basis of comparison in the year-earlier period, when a profit from a stock transaction at its iron ore affiliate in Chile helped boost its results.

Revenue increased 4.5% to JPY 10.009 trillion from JPY 9.581 trillion a year earlier on higher oil prices. But operating profit fell 15% to JPY 168.61 billion.