Feb 23 (Reuters) - Australian shares fell on Thursday, dragged by weakness in the materials sector with miner Rio Tinto tumbling after going ex-dividend, though rises in Qantas Airways and Casino operator Crown Resorts after their earnings contained losses.
The S&P/ASX 200 index was down 0.4 percent, or 22.399 points, at 5,782.700 by 0044 GMT. The index saw its biggest fall in over 3 weeks during the session.
"Australian market is in reporting season, with a lot of stocks going ex-dividend. Rio Tinto has gone ex-dividend as well. That coupled with a weak lead from U.S. is why stocks are down," said Gary Burton, market analyst at IG Markets.
Rio Tinto fell as much as 4.9 pct for its biggest fall in over three months, with about 5.9 million shares changing hands, 2.4 times the 30-day average volume.
BHP Billiton, which has substantial oil interests, slid 2.7 percent, on the back of lower copper and oil prices.
The earnings season kept markets on edge, with a fair share of disappointments in the past week.
Qantas Airways provided some cheer with its earnings, with the stock rising as much as 6.5 pct to a 10-month high after half-year underlying pre-tax profit beat company's guidance range.
Casino operator Crown Resorts Ltd touched its highest in four months, after its first-half net profit rose 75 percent, helped by sales of stakes in resorts in Macau and Las Vegas.
On the negative ledger, the country's biggest listed travel agent, Flight Centre Travel Group Ltd, fell to an over 4-year low after cutting guidance and reducing dividend.
Ardent Leisure Group touched a 3-1/2 year low. The company reported loss for half year due to A$93.6 million writedown on its Dreamworld operations, which saw slump in attendance after last year's fatal accident which killed four people.
Elsewhere, Santos dropped 1.6 percent and Origin Energy slid 2.2 percent, after oil prices fell on expectations of another surge in U.S. inventories.
New Zealand's benchmark S&P/NZX 50 index rose 0.28 percent, or 19.54 points, to 7,082.02.
Telecom and materials stocks gained, with Fletcher Building and Spark New Zealand rising 1.9 percent and 1.4 percent, respectively.
Spark's rival Sky Network Television slumped to a near 8-year low after competition watchdog rejected Sky's purchase of Vodafone's New Zealand unit.
Reporting by Suhail Hassan Bhat; Additional Reporting by Ambar Warrick in Bengaluru; Editing by Shri Navaratnam