Mining giant BHP Billiton today said it planned to invest billions of dollars in expansion of its coal and iron ore operations in Australia.

The cash-heavy resource giant said it would pump $7.4 billion into continuing production growth in the company's Western Australia iron ore operations to ratchet up capacity to over 220 million tonnes a year.

Of these, $3.4 billion would go toward development of its Jimblebar mine and rail links, and in the purchase of mining equipment and rolling stock.

Another $2.3 billion has been allocated for improvements to Port Hedland, that include extra berths and shiploaders, a car dumper, rail works as also rolling stock.

The rest of the investment would go toward improvement of port blending facilities and rail yards. BHP would contribute $6.6 billion to the projects while its partners would chip in with the rest.

The Melbourne-based Anglo-Australian mining giant also announced a $5 billion cash injection into three key metallurgical coal projects in Queensland's Bowen Basin, with BHP's share $2.5 billion.