The dollar set an eight-week low against the yen on Friday as escalating tensions between the United States and North Korea triggered yet more investor flight to safety.
The dollar slipped to as low as 109.11 yen JPY= in early Asian trade on Friday, its lowest level since June 14, when the greenback had fallen to as low as 108.81 yen.
Below that level lies another key support level for the dollar on technical charts at 108.13 yen, a trough the greenback touched in mid-April.
"We're getting close towards very important support on the dollar/yen," said Steven Dooley, currency strategist for Western Union Business Solutions in Melbourne.
"Particularly that 108.10/108.00 level, a break below those levels would really set up a rapid move to the downside," he said.
On Thursday the greenback had shed 0.8 percent versus the yen, with the Japanese currency rallying broadly against most major currencies.
Both the Swiss franc and the yen have climbed against the dollar this week, after US President Donald Trump warned North Korea that it would face "fire and fury" if it threatened the United States.
Trump ratcheted up his rhetoric against North Korea and its leader on Thursday, warning Pyongyang against attacking Guam or US allies after it disclosed plans to fire missiles over Japan to land near the US Pacific territory.
"The yen is the big story really. Risk aversion is still very much a concern for markets," said Shaun Osborne, chief currency strategist at Scotiabank in Toronto.
The Swiss franc and Japanese yen are often sought in times of geopolitical tension or global financial stress, partly because both countries have big current account surpluses.
Japan is the world's biggest creditor nation and there is an assumption Japanese investors may repatriate their foreign holdings in times of heightened global uncertainty.
Later on Friday, investors will look to US July consumer price data for hints on the Fed's policy outlook and near-term moves in the dollar.
Subdued US inflation has stirred doubts about the chances of another Fed interest rate hike this year, weighing on the greenback.
The euro eased 0.1 percent to $1.1766 EUR=, staying below a high of around $1.1910 set last week, the euro's strongest level in 2-1/2 years.