Japanese government officials on Friday pledged to take "appropriate measures" as the surging yen fuels speculation that the central bank will intervene in currency markets to arrest its ascent.
The unit has soared to levels last seen when the Bank of Japan unleashed a second wave of stimulus in late 2014, as part of Tokyo's attempts to stimulate the laggard economy.
But plunging equity markets fuelled by fears about the world economy have sent the yen skyward as traders buy investments seen as a safe bet -- pushing the unit towards its biggest two-week advance since the 1998 Asian financial crisis, according to Bloomberg News.
On Friday, Japanese officials declined to say if the BoJ had intervened in currency markets for the first time since 2011.
But "there have been some rough price movements so we are watching the market closely and will take appropriate measures if necessary", finance minister Taro Aso said.
Government officials declined to elaborate on what sort of measures Tokyo might take, but said they would discuss currency rates at a G20 meeting later this month.
BoJ governor Haruhiko Kuroda called the market reaction "excessive, given that the fundamentals of the Japanese economy" are steady.
He made the comment before meeting with Prime Minister Shinzo Abe Friday, local media reported.
Japan reports fourth-quarter economic growth data on Monday, with many expecting a contraction. (AFP)