The yen fell to a fresh 34-year low against the dollar, but rapidly rebounded on Monday. The volatile moves have led to speculation that Japanese authorities intervened in the currency market.
The market is closed in Japan for a national holiday. But trading is held as usual elsewhere.
In Asian markets, the yen initially traded at the lower-158 level and fell further on Monday morning, reaching 160 for the first time since April 1990.
Less than three hours later, the yen bounced back to the 154 to 155 level.
Market players say there is speculation that the Japanese government and the Bank of Japan intervened. That's because the yen's surge came even though there are no clear incentives for investors to buy it.
Vice Finance Minister for International Affairs Kanda Masato declined to comment on the developments.
The yen also briefly fell to the lowest level against the euro since the single currency was introduced in 1999.