Australian shares were flat on Wednesday as investors took a...

Australian shares were flat on Wednesday as investors took a cautious stance ahead of the Britain's EU referendum, while weak commodities capped gains.

The S&P/ASX 200 index (xjo) was up 0.03 percent, or 1.3 points at 5,275.70 by 0155. The benchmark rose 0.3 percent on Tuesday.

"The looming vote on Brexit is creating a high level of uncertainty in the markets, to say the least, with both US and European markets experiencing volatile sessions overnight," said Gary Huxtable, client adviser at Atlantic Pacific Securities.

"Market participants are unwilling to hold overnight risk. It would be very surprising if this mentality didn't continue in our market over the next couple of days."

Gold miners were among the main laggards on the index on Wednesday with Evolution Mining (EVN) and Regis Resources (RRL) dropping more than 4 percent each on weak gold prices.

Major miners BHP Billiton (BHP) and Rio Tinto (RIO) added 0.6 percent and 1.4 percent respectively.

The "Big Four" banks were in the black with ANZ Banking (ANZ) the strongest performer, rising 1 percent. Westpac (WBC) rose 0.6 percent while National Australia Bank (NAB) and Commonwealth Bank (CBA) were up about 0.2 percent each.

U.S. stocks ticked up on Tuesday as Federal Reserve Chair Janet Yellen took a relatively optimistic stance on the economy and played down the risk of a recession. New Zealand's benchmark S&P/NZX 50 index (nz50) fell 0.5 percent or 31 points to 6.808.77 as investors continue to tread water ahead of the referendum in Britain.

First NZ Capital Broker Philip Hunter noted that some offshore investors "have stuck to the sidelines, distracted by things in the European area."

The biggest gainers included Comvita (CVT), up 1.6 percent. Spark (SPK), which earlier in the day said it is now the number one mobile company in terms of revenue earned from customers, tacked on 0.4 percent.

The biggest losers included outdoor clothing retailer Kathmandu (KMD). The stock was off 2.2 percent and Hunter said investors are likely concerned about the unseasonably warm weather in New Zealand.

"Kathmandu needs a bit of a cold snap to get the tills going," said Hunter.