United States gold futures for December delivery rose 0.2 percent to $1,281.20 per ounce.
Investors also took cover in the yen, the Swiss franc and gold.
Stocks are opening slightly lower on Wall Street after several companies reported disappointing results.
The yen tends to benefit during times of geopolitical or financial stress as Japan is the world's biggest creditor nation and there is an assumption that Japanese investors there will repatriate funds should a crisis materialise. It's experienced the biggest weekly rise since December 2015.
"That may have weighed a little bit" on markets, said Phil Guarco, global investment specialist J.P. Morgan Private Bank. But Mellor notes the rhetoric has reached a "different level".
USA stock indexes were set to open little changed on Friday, with the S&P 500 on track to post its biggest weekly loss in nine months, as investors remained cautious on heightened tensions between the United States and North Korea.
Technology conglomerate Toshiba was 3.2% higher, paring back gains of as much as 6% earlier in the session, as traders continued to celebrate the fact the firm's auditor was about to sign off its much-delayed annual numbers. The euro zone's version is at its highest since April, when France's election was rattling the region.
S&P 500 e-minis were up 1.5 points, or 0.06 percent, with 300,073 contracts traded.
'Of course, it's all come at a time when share markets are due for a correction, so North Korea has provided a ideal trigger'. Euro/dollar edged up from 1.1747 to 1.1754, while the yen gained the most, with dollar/yen sinking by 0.37% to an eight-week low of 109.31. 'Pretty remarkable, perhaps even extraordinary, considering, ' said Tim Ash, strategist at fund manager BlueBay.
At 12:36 p.m. ET (1636 GMT), the Dow Jones Industrial Average was down 158.98 points, or 0.72 percent, at 21,889.72 and the S&P 500 was down 27.37 points, or 1.11 percent, at 2,446.65.
The unease about the relationship between the US and North Korea was more prominent in other markets, several market strategists said.
Yes, the VIX volatility index remains historically low at just 15.4.
The financial sector index (.SPSY) gave back gains after news California insurance regulator will probe whether Wells Fargo & Co (WFC.N) and an insurance company harmed residents by selling insurance they did not need.
Crude futures meanwhile extended losses on fears of slowing demand and lingering concerns over global oversupply. The Nasdaq added 39.68 points, or 0.6 percent, to 6,256.56. The Nasdaq composite fell 45 points, or 0.7 percent, to 6,324. Netflix also fell, giving up $2.58, or 1.4 percent, to $175.78.
The remarks followed a new report asserting that US intelligence has assessed that Pyongyang has successfully produced a nuclear warhead that can fit inside its missiles.