South32 Ltd. will return a further US$500 million to shareholders via an on-market share buyback in Australia.

"Our net cash balance continues to build giving us the financial strength and flexibility to invest in our existing operations, pursue opportunities where we can create value and return excess capital to shareholders," CEO Graham Kerr said March 27.

In mid-February, South32 revealed it would pay its first half-yearly dividend of 3.6 U.S. cents per share, for a total of US$192 million, after booking an after-tax profit of US$620 million for the first half of fiscal 2017.

South32 said the share buyback, which will be completed over a 12-month period, is not subject to shareholder approval and will be funded from existing cash reserves.

The timing and number of shares purchased will be contingent upon the prevailing share price and market conditions.