The Indian rupee and the Chinese yuan failed to benefit from slight optimism on the region, according to the survey of 22 fund managers, analysts and currency traders conducted from Tuesday through Thursday.

Britons on Thursday cast ballots in a historic EU membership vote. The campaign to stay in the union got a boost from two opinion polls published on Wednesday, but the result was widely considered too close to call.

A victory for the "Remain" camp could spur investors to seek more risky assets, including emerging Asian currencies, especially after the Fed took a cautious stance on monetary policy tightening.

Fed Chair Janet Yellen on Tuesday said the central bank's ability to raise interest rates this year hinges in part on whether Britain votes to leave the EU and if there's a slowdown in U.S. hiring.

In the poll, the Indonesian rupiah was one of a main beneficiaries in emerging Asia, with its bullish bets rising to a more than three-month high.

Foreign investors bought the country's bonds, which offer one of the highest yields in the region. The central bank last week slashed interest rates and its deputy governor indicated further easing, raising appeals of capital gains.

Sentiment on South Korea's won turned bullish, for the first time in almost two months, on bond inflows amid expectations of a further interest rate cut there.

Mounting caution ahead of the British vote boosted demand for the Singapore dollar . The currency's bullish bets increased to the largest since mid-April.

Investors squared positions on some emerging Asian currencies, rather than making fresh bets.

Sentiment on India's rupee turned bearish. The currency fell to a near one-month low after central bank governor Raghuram Rajan announced he would quit when his three-year term ends in September.

Rajan, a former International Monetary Fund chief economist, has been popular with foreign investors due to his efforts to tackle inflation and rescue India from its worst financial crisis in more than two decades.

Bearish bets on China's yuan ticked up as the renminbi hit a more than five-year low last week. That came after China failed again to convince U.S. index provider MSCI Inc to add local Chinese shares to its key emerging market index.

Sentiment on the yuan has remained pessimistic as the world's second-largest economy has not shown clear signs of a recovery yet.

The poll is focused on what analysts and fund managers believe are the current market positions in nine Asian emerging market currencies: the Chinese yuan, South Korean won, Singapore dollar, Indonesian rupiah, Taiwan dollar , Indian rupee, Philippine peso , Malaysian ringgit and the Thai baht .

The poll uses estimates of net long or short positions on a scale of minus 3 to plus 3. A score of plus 3 indicates the market is significantly long U.S. dollars.

The figures include positions held through non-deliverable forwards (NDFs).

(Additional reporting by Shaloo Shrivastava in BENGALURU; Editing by Richard Borsuk)

By Jongwoo Cheon