Global mining giant Rio Tinto Ltd gets further push on its aim to corner a sizeable chunk of Africa's coal resources as the resource firm's $3.9 billion takeover proposal won the stamp of approval from Riversdale Mining Ltd's board of directors.

In a statement released on Monday, Riversdale executive chair Michael O'Keefe announced the directors affirmation of Rio Tinto's bid for the Australian collier as he explained that "the directors consider that the offer, by crystallising value now for the company's shareholders' investment in Riversdale, provides an attractive alternative to holding their Riversdale shares."

Rio Tinto tossed an all-cash proposal to acquire Riversdale Mining that leaves the junior miner to consider a share offer bid of $16, which analysts said is relatively below the target company's current share value of $16.47 as of Monday's share market opening.

Also, industry watchers are anticipating more developments on the possible merger of Rio Tinto and Riversdale as reports emerged that a state-owned Indian consortium is seriously considering a rival bid that could derail the mining giant's coal agenda in Africa.

Both India and Rio Tinto are scrambling to capture considerable amount of coal resources in the continent in anticipation of the rising market price of thermal and coking coals in the coming years.

Riversdale came out as a juicy target for its Benga and Zambeze coal projects in Mozambique, which the collier's board of directors has acknowledged are yet to achieve full production capacity.

Yet the projects' present conditions failed to deter the enthusiasm of Rio Tinto and its possible competitors in securing the coal resources, which experts said would definitely reach optimum production capability.

Despite talks of support coming from India's Tata Steel, which maintains more than 24 percent interests on Riversdale Mining, for the proposal said to be introduced by the state-backed Indian group, Riversdale's board went ahead on its recommendation for Rio Tinto's bid to the target firm's shareholders.

O'Keefe said that Riversdale has yet to receive any serious bids from any entity as he stressed that "as of today, no superior proposal has been received by Riversdale and the company is not aware of any party having an intention to make such a proposal."