TOKYO: Asian shares stepped back on Friday while investors poured funds into safe-haven assets amid festering concerns about a UK referendum that could push Britain out of the European Union.

MSCI's broadest index of Asia-Pacific shares outside Japan .MIAPJ0000PUS dipped 0.2 percent while Japan's Nikkei .N225 declined0.4 percent.

Wall Street shares also pulled back on Thursday after three days of gains, with the S&P 500 .SPX losing 0.17 percent to finish at 2,115.48, still only about 15 points below its record closing high.

Global bond yields dropped to new lows and perceived safe-haven currencies gained as investors sought shelter in the safety of bonds on concerns about Britain's referendum on European Union membership on June 23.

"There are concerns over 'Brexit' as polls seem to suggest the probability of Britain leaving Europe is rising," said Tatsushi Maeno, managing director at PineBridge Investments.

"You can't buy risks assets under such conditions even if you want to," he said.

German 10-year Bunds yield also hit a record low of 0.024 percent DE10YT=RR while the 10-year British gilt yield GB10YT=RR struck an all-time low of 1.224 percent.

The European Central Bank's commencement of its corporate bond purchase program also bolstered European bonds.

In Japan, the 10-year government bond yield slipped to a record low of minus 0.140 percent JP10YTN=JBTC.

The 10-year US Treasuries yield US10YT=RR broke out of its trading range since March to hit a 3 1/2-month low of 1.659 percent on Thursday. It last stood at 1.685 percent.

The US bonds were also helped by expectations that the Federal Reserve will refrain from raising interest rates next week or at the July meeting following a surprisingly weak US employment report last Friday.

"Investors who had been waiting for a Fed rate hike gave up on waiting and started buying," said Tomoaki Shishido, fixed income analyst at Nomura Securities.

The spectre of low interest rates and fear of "Brexit" lifted gold XAU= to a three-week high of $1,271.70 per ounce.

In the currency market, the Swiss franc gained 1.6 percent over the past five days, its biggest five-day gain since March 2015, hitting a eight-week high of 1.0886 franc per euro EURCHF=. It last stood at 1.0910.

The low-yielding yen JPY=, which tends to be bought back when risk appetite suffers, stood at 107.02 per dollar, clinging near five-week highs of 106.26 set on Thursday.

The euro EUR= eased to $1.1315 from a four-week high of $1.1416 set on Thursday

The British pound GBP=D4 was on edge at $1.4463, having slipped from this week's high of $1.4664 touched on Tuesday.

Although it has stayed 4.5 percent above its seven-year low set in late February, investors are actively seeking protection against a slide in the event of Brexit.

The cost of hedging against swings in sterling's exchange rate over the next month soared, with sterling's one-month implied volatility GBP1MO= hitting its highest in more than seven years.

Oil prices also stepped back after notching another 2016 high.

Still, persistent threats by militants against Nigeria's oil industry and fear of more security incidents that could hit supplies worldwide limited losses in crude.

Global benchmark Brent crude futures LCOc1 traded at $51.86 per barrel after having risen to as high as $52.86 on Thursday.