Australia's Rio Tinto Mining Ltd has strengthened its bid obtaining 49.49 percent of all the shares of Riversdale Mining Limited (Riversdale), the company announced late Wednesday.

Rio Tinto's subsidiary Rio Tinto Jersey Holdings 2010 Limited (RTJ) was successful in securing the remaining shares that would allow the company as the majority shareholder in Riversdale, the coal miner based Mozambique.

"As a result, RTJ has now increased the Offer price under its takeover Offer (Offer) for Riversdale to $16.50 cash per share. Given the Offer is now unconditional. Riversdale shareholders who have accepted the Offer on or before today's date will be paid the Offer price of $16.50 per share by 13 April 2011.

"Riversdale shareholders who accept the Offer after today's date will be paid the Offer price of $16.50 within five business days of that acceptance being received.

Also, in accordance with section 624(2) of the Corporations Act (as modified), the Offer period has been automatically extended for a period of 14 days as a result of the Offer price increase, so that it will now end at 7.00pm (Sydney time) on Wednesday, 20 April 2011 (unless further extended)," the company said in an emailed statement.

Rio is believed to have brokered the deal with Brazil's biggest steelmaker CSN for the crucial shares it needs to complete its bid. The other major shareholder is Tata Steel of India.

Rio's shares in the ASX failed to take this development into stride as it dropped 17 percent at morning trade in Sydney to $85.95 per share as of 11:49 AM.

More from IBT Markets:
Newsletter: To receive Global Markets update, sign up here