"We have maintained our emphasis on efficiency and protecting returns, which is reflected in this solid production performance," Rio Tinto chief executive Sam Walsh said.

"We have also delivered three significant achievements within our growth portfolio

"Our combination of world-class assets, financial strength, and operating and commercial excellence provides a sound base to continue to generate sustainable returns for our shareholders."

Rio Tinto Alcan Yarwun processes alumina using the four-stage Bayer process.

Highlights:

• Iron ore production and shipments in the first half increased compared to last year despite severe and unseasonal weather in the Pilbara throughout the first half.

• Second quarter production of iron ore was nine per cent higher than the same quarter of 2014 and was seven per cent above the first quarter of 2015.

• The key elements of the Pilbara 360 Mt/a infrastructure expansion are complete.

• The focus is now on generating maximum value from the assets, including debottlenecking and productivity improvements.

• The modernised Kitimat aluminium smelter in Canada poured first hot metal during the quarter.

• The progressive ramp up of production towards nameplate capacity of 420 thousand tonnes is expected to complete in early 2016. The modernised smelter will substantially increase output and lower production costs and emissions.

• The signing of the Oyu Tolgoi Underground Mine Development and Financing Plan (UDP) on 18 May 2015 represents a significant step forward for the project.

• The UDP between the Government of Mongolia, Turquoise Hill Resources and Rio Tinto provides a pathway forward in addressing shareholder matters to restart underground development. Next steps include approval of the underground feasibility study and project financing, as well as obtaining necessary permits.