Sterling hit a 2016 high and the euro surged against the dollar and yen on Thursday after a series of late opinion polls favoured Britain staying in the European Union and bookmakers odds indicated a further shift towards the "Remain" camp.

"The market is clearly now pricing in, with near certainty, a "Remain" vote... I do think a "Remain" vote is more likely, but not with the degree of certainty that appears to be now priced," said Adam Cole, head of G10 currency strategy at RBC Capital Markets.

The pound, and to a lesser extent the euro, have been buffetted since February, by opinion poll results which have swung from predicting a clear victory for the government-led "In" camp to a narrow vote for a "Brexit".

However, gold fell to a two-week low as the last sweep of opinion polls before Britain's referendum on EU membership began gave the campaign to stay in the bloc a slight edge.

Spot gold was down 0.2 per cent at $1,263.26 an ounce by 1149 GMT on Thursday, after hitting $1,258.25, its lowest since June 9.

The metal, often perceived as a hedge against economic and financial uncertainty, reached a near two-year high on June 16, as wider markets reacted to mounting concerns over the prospect of Britain pulling out of the EU and sought protection in 'safe' assets.

They also included German bunds, the Swiss franc and Japan's yen, but the rally was short-lived.

Odds on the Betfair betting exchange have slumped from 40 per cent last Thursday before the killing of pro-EU lawmaker Jo Cox to just 14 per cent on Thursday. But the final polls still remain within the margin of error.

"The early results are potentially going to be very confusing," Cole said. "If this is the starting point (with which) we go into the 10 o'clock polls and the results, there's a lot of scope of volatility, to the downside."

Sterling is up around 4 per cent this week but the options market shows record levels of uncertainty about its fate over the next 24 hours.

Overnight sterling implied volatilities were quoted as high as 125 per cent, levels at which traders said it was effectively impossible for fund and corporate buyers to trade. It dropped towards 40 percent around mid-day as the currency rallied.

Voting will end at 2100 GMT (2200 BST), with results expected early on Friday. Pollster YouGov will publish a poll of how people have voted shortly after polling stations close, hoping to repeat its successful prediction of the 2014 Scottish independence vote.

Banks have warned clients about volatile trading conditions around the results which may lead to large gaps in prices. Barclays stopped accepting new "stop loss" orders as of 0600 GMT, an extremely rare move for one of the big six banks that dominate the world's biggest financial market.

"These are very challenging conditions," said Yujiro Goto, currency strategist at Nomura, warning of a sharp fall in sterling if there are signs of a "Leave" vote after polls close.

Rising expectations that Britain would vote to stay in the EU bolstered overall risk sentiment, helping higher-yielding currencies and dampening demand for safe-haven currencies like the yen and the Swiss franc.-Reuters