By Alastair Sharp

TORONTO (Reuters) - Canada's currency and shares of most of its largest companies weakened in the wake of Britain's vote to leave the European Union on Friday, while government bond yields slipped as investors bet the Bank of Canada will cut interest rates.

The threat to global growth that the so-called 'Brexit' presents will prove a headwind for an economy that relies on energy and other commodity exports, analysts and investors said.

"It increases the risk that deflation could take hold," said Patrick O'Toole, vice president of global fixed income at CIBC Asset Management, adding that the result called into question the EU's existence.

Oil prices, which have doubled since February, fell about 5 percent after the vote and Canadian energy stocks shed more than 3 percent. [O/R]

To be sure, some equity analysts saw the sharp decline as a buying opportunity.

"This is just a bump in the road," Brian Pow, an equity analyst at Acumen Capital Partners in Calgary. "I still think the trend is upwards in crude prices, it just might take longer."

Banking and other financial stocks joined energy stocks in taking the brunt of the selling pressure in Canada, while gold miners benefited from investors fleeing to the safety of bullion. [.TO][GOL/]

Gold stocks helped Canada outperform, with the market down roughly 1.5 percent compared to 3 percent for major U.S. indices.

Some saw the retreat as a buying opportunity, noting that limited direct exposure to Europe and a strong trade relationship with the United States should help Canadian assets weather the storm.

"We remain at the ready to swoop in and buy stocks in these volatile times," said Stephen Carlin, head of equities and portfolio manager at CIBC Asset Management.

Canada's currency was heading for its sharpest move lower against the greenback in more than a year. [CAD/]

It also retreated against the Japanese yen and Swiss franc, traditionally seen as safe havens, though it surged almost 8 percent against the British pound and climbed against the euro.

Yields on two-year government bonds, seen as particularly sensitive to potential monetary policy shifts, fell as low as 0.386 percent before recovering somewhat.

Overnight index swaps moved to imply a 27 percent chance of a Bank of Canada rate cut this year, after having been priced for no change in policy before the Brexit result.

Bond prices were much higher across the maturity curve in sympathy with Treasuries as investors rushed into safe-haven assets.

(With additional reporting by Fergal Smith in Toronto)