SYDNEY/WELLINGTON, June 23 (Reuters) - Australian shares inched higher on Thursday as the latest opinion polls suggested Britain would stay in the European Union, though the vote was so close it kept all but the bravest investors on the sidelines.
The S&P/ASX 200 index .AXJO firmed 0.2 percent or 11.2 points to 5,282.2 by 0400 GMT. The market has been in limbo for much of the week in the countdown to the UK poll, which is due to close at 2100 GMT.
The latest YouGov opinion poll for The Times newspaper showed the "In" camp led "Out" by 51 percent to 49 percent, while a ComRes poll put the "In" lead at 48 percent to 42 percent.
Analysts fear turmoil in global markets should the country actually vote to leave, with risk assets such as stocks and the local dollar likely to take a big hit.
Helping miners was a $1 a tonne jump in iron ore prices and the basic materials sector was the biggest gainer of the day with an increase of 1.2 percent.
Fortescue Metals FMG.AX put on 5.4 percent to reach its highest in two months, and is up around 75 percent for the year so far.
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New Zealand's benchmark S&P/NZX 50 index .NZ50 was up 0.7 percent or 46 points at 6,827.61, again as fears Britain might leave the EU ebbed slightly ahead of the referendum.
The biggest gainers were Air New Zealand AIR.NZ up 1.9 percent and Spark SPK.NZ up 1.5 percent. Volumes, however, were very light.
The biggest losers were Nuplex NPX.NZ which shed 1.9 after the company said Allnex Belgium SA has advised Nuplex that the review process for receiving anti-trust clearance in the European Union is taking longer than expected. Allnex made a $1.05 billion offer for Nuplex earlier this year.
Shareholders are due to vote on the scheme of arrangement at a special meeting in Auckland on July 7.