The value of the yen against the dollar dropped to the upper-160 range at one point in New York on Wednesday -- a level not seen in over 37 years.
The yen also fell against the euro to the upper-171 range at one point -- the lowest since the European currency was introduced in 1999.
A view that the US Federal Reserve is in no hurry to cut interest rates spread among investors on Wednesday after a senior Fed official expressed a cautious stance about an early rate cut on Tuesday.
In response, investors sold the Japanese currency at the London exchange, pushing it below the level of 160.24 marked in late April -- to its lowest standing since December 1986.
Japan's currency chief, Vice Minister of Finance for International Affairs Kanda Masato, told reporters on Wednesday night that necessary steps will be taken against excessive moves.
But the yen's selling continued at the New York exchange. The currency depreciated to the upper-160 range at one point.
Market sources pointed out the yen has passed the 160.24 mark against the dollar, and that many investors see the official's comment as lacking strength. They said that prompted speculators to accelerate their yen selling.
The sources also said there is a strong view that even if the government and the Bank of Japan intervene in the market, any effect will be temporary.