Tata Steel Global Minerals has increased its stake in Australian mining firm Riversdale Mining to 19.38% by purchasing an additional 8.5 million shares worth around Rs2.13bn.

Tata previously said that because of the rapid increases in the costs of raw materials such as iron ore and coking coal it is keen to achieve raw material security.

Riversdale has acquired coal exploration tenements in Mozambique, with a combined size in excess of 250,000ha and Tata is already in a $100m agreement for a 35% stake in two of these tenements, gaining access to 40% of the coal produced from the projects, expected to start after 2014.