Australian shares ended flat on Wednesday as gains in miners were offset by profit-taking in the healthcare sector, while New Zealand's market was hit by steep looses for energy stocks after Rio Tinto said it plans to shut a power-guzzling smelter.

The benchmark S&P/ASX 200 index was little changed at 6,673.10 points, having advanced 0.3% on Tuesday.

Healthcare firms were the among the worst performers, falling as much as 1.5% during the session before ending 0.4% lower.

"It's simply a bit of profit-taking or rebalancing of portfolios right now in the health space," said Brad Smoling, managing director at Smoling Stockbroking.

Buying of defensive stocks has pushed the sector up nearly 30% this year, making it one of the top gainers on the ASX 200.

Australia-listed shares of Resmed Inc declined 2.7%, while Sonic Healthcare lost and Pro Medicus lost 1.3% and 6.1%, respectively.

Financial stocks were slightly lower, with No. 2 lender Westpac Banking Corp falling 0.2%. The bank said its cash earnings in the second half of 2019 would be reduced by about $233 million due to customer remediation programmes.

In the mining sector, heavyweight Rio Tinto Ltd rose 0.4% after it flagged a possible pullback or closure of an "unprofitable" aluminium smelter in New Zealand.

Fortescue Metals Group ended up 2.2%, a day before it is due to report its first-quarter production results.

Gold stocks rose 0.3%, as bullion prices inched up from increased tensions over Brexit.

Miner Gold Road Resources Ltd rocketed 12% and was the largest gainer on the ASX 200 after RBC upgraded the stock.

New Zealand shares clocked their worst intraday session in more than two months, as utilities were stung by Rio Tinto's plan to shut its aluminium smelter, the largest single power consumer in the country.

The benchmark S&P/NZX 50 index declined 2.1% or 236.60 points to 10,853.79.

Meridian Energy Ltd slid nearly 8.7% to a near two-month closing low. The company is the main supplier of electricity to the Rio Tinto smelter.

Peers Contact Energy Ltd and Mercury NZ Ltd fell 9.7% and 8.4%, respectively.

Brokerage UBS in a note said that closure of the site "would have significant short, medium and long term consequences across the New Zealand utilities space and more broadly for New Zealand".