"It's a clear case of "risk-off" sentiment lifting the yen, as investors focus on the latest developments with North Korea", said Kumiko Ishikawa, FX market analyst at Sony Financial Holdings in Tokyo.
The dollar index fell 0.14 per cent, with the euro unchanged at US$1.1757. The Swiss franc is up close to 1.5%, its strongest one-day rise since 2015, and gold is up 1% to $1275 per ounce, its highest level for eight weeks. When the rhetoric between the two leaders heated up, investors were scurrying for safe haven currencies, including the Yen and the Swiss Franc, which surged about 1.1% on Wednesday.
South Korea's won dropped 0.9 per cent against the U.S. dollar to its lowest close since July 13.
But despite the largest percentage drop in over a month on a global equities index, United States equities ended only slightly lower as healthy corporate earnings and a recent string of strong economic data enticed investors into beaten-down stocks.
Gold prices were nudged away from recent highs as broader risk aversion receded somewhat.
Against the dollar, the franc surged 0.6 percent to 0.9688 francs, reversing a two-week losing streak.
Money moved to the relatively safer bond markets after President Donald Trump threatened North Korea on Tuesday with "fire and fury like the world has never seen". Sterling was last trading at US$1.3006, up 0.02 per cent on the day. The USD/JPY pair was trading at 110.072 Yen, up 0.13%. "The sell-off caused by geopolitical tensions on North Korea will likely be short-lived as long as both Trump and Kim Jong Un keep making feints against each other and neither takes military action", said Tomoaki Fujii, head of the investment research division at Akatsuki Securities Inc in Tokyo.
The euro EURUSD, -0.3146% dipped to $1.1721, compared with $1.1760 late Wednesday in NY.
Benchmark US 10-year notes rose 9/32 in price to yield 2.2494 per cent, from 2.282 per cent late on Tuesday.
Gold rose 0.6% to $1,268 (£976) an ounce and platinum gained 0.6% to reach $972.95 an ounce, having hit its highest since April at $979.
German and US sovereign bond prices also rose on the fear trade, sending yields lower despite recent strong readings of economic growth. The Nasdaq composite lost 0.3 percent to 6,352.33.
Brent crude was flat at $52.70 a barrel.