RPT-CORRECTED-UPDATE 1-Nyrstar H1 results below expectations

(Corrects percentage change in first paragraph to 77 percent from 45 percent; EBITDA in second paragraph to 81 million from 106 million; revenue in third paragraph to 1.408 billion from 1,408 billion; repeats to add UPDATE 1 in headline) BRUSSELS, Aug 19 (Reuters) - Belgium's Nyrstar (NYR.BR), the world's biggest producer of zinc, reported on Tuesday a worse- than-expected 77 percent drop in first-half core profit due to lower zinc prices and a weaker dollar.

Earnings before interest tax, depreciation, and amortisation (EBITDA) for the first half of 2008 amounted to 81 million euros ($156.1 million), against 358 million euros in the same period last year, while a Reuters poll of analysts gave an average estimate of 138.4 million euros.

Revenue declined 18 percent to 1.408 billion euros.

The company did not mention the possibility of launching a share buyback scheme, a move which was expected by a number of analysts as a way to boost its ailing share price.

Nyrstar, which floated at 20 euros a share in October, has lost more than half its value since then and is currently trading at just over 7 euros.

"Despite a falling zinc price and weakening dollar exchange rate, we have continued to focus on managing factors that are within our control," Chief Executive Paul Fowler said in a statement.

"Through a combination of prudent and disciplined management we have improved production of both zinc and lead metal and maintained largely flat costs in an inflationary environment."