BlackRock Inc. said on Friday it had suspended the issuing of shares in its physically backed gold exchange-traded product due to a historic surge in buying as global economic uncertainty rekindled bullion's safe-haven appeal among investors.

BlackRock anticipates it will be able to resume issuing more shares by Tuesday or Wednesday, according to a person familiar with the matter.

IAU, or iShares Gold Trust, has seen its assets under management surge by $1.4 billion to $8 billion since the start the year. February marked the biggest spurt of demand in the last decade, BlackRock said.

Holdings in major gold ETFs have zoomed 20 percent since the start of the year, hitting almost 48 million ounces this week, their highest since September 2014.

While the BlackRock move appears to be an isolated case, it illustrates the voracious demand for bullion as economic uncertainty, a weak dollar and falling expectations for U.S. interest rate hikes have spurred the biggest buying spree of gold ETFs in five years and helped prices rally to their highest in 13 months.

Interest in Sprott Management Asset's gold-backed trust has also risen but is not in danger of running out of gold, said John Wilson, chief executive of Sprott Asset Management in Toronto.

"We don't have the issue where people show up and we can't satisfy the demand for them," Wilson said, adding that the units closed at a 0.1 percent premium on Thursday. "In our case, if you want to buy physical gold, you put in an order and there are people who are selling."