Adds shares in paragraph 2, production details in paragraph 4, forecast in paragraphs 8-10

Feb 20 (Reuters) - Australia's Whitehaven Coal WHC.AX reported better-than-expected first-half earnings on Thursday, helped by higher production and sales due to strong contributions from its mines in New South Wales.

Shares of the company were up 8.2% by 0109 GMT, and were among the best performers on the benchmark ASX 200 index .AXJO, which was down 1%.

"Operational performance at Daunia and Blackwater – and across our NSW mines – has been in line with or better than plan, and demand for Whitehaven's metallurgical and thermal coal products continues to prove strong," CEO Paul Flynn said in a statement.

Whitehaven posted first-half saleable coal production at 15 million metric tonnes, compared with 8.6 million tonnes a year earlier.

The coal miner said revenue for the six months ended December 31, nearly doubled to A$3.4 billion ($2.16 billion) from A$1.6 billion last year.

The average price for coal sold during the half-year also rose 5% to A$232 per tonne.

Underlying net profit after tax was A$328 million ($208.15 million) for the six months, significantly ahead of the Visible Alpha consensus of A$219 million.

Whitehaven said its run-of-mine coal production and coal sales were on track to be in the upper half of its fiscal year 2025 forecast, while its unit cost of coal was tracking to stay at the low end of forecast range.

It, however, said the incremental demand in coal markets has been relatively soft in fiscal 2025, and the rebound in Indian demand for metallurgical coal has been slower than expected.

Whitehaven added it was focused on "optimising margins through the cycle," but did not provide details.

The firm declared an interim dividend of 9 Australian cents apiece, higher than consensus estimate of 7.6 cents.

($1 = 1.5763 Australian dollars)

(Reporting by Nichiket Sunil and Rishav Chatterjee in Bengaluru, Editing by Mohammed Safi Shamsi and Varun H K)

((Nichiket.Sunil@thomsonreuters.com; Rishav.Chatterjee@thomsonreuters.com))