On Friday, Japan warned against sharp falls in the yen, and expressed concern over the moves in a rare joint statement by the government and the central bank, leaving investors wary about the potential for intervention.
It has been more than a decade since Japan intervened directly in the foreign exchange market and more than two decades since it intervened to support its currency.
Here is a timeline of the moves in the FX markets by the Bank of Japan.
Japanese monetary authorities decided to let the yen float freely against the dollar in 1973.
In February six of the G 7 nations signed the Louvre Accord, which aims to stabilise currencies and halt the decline of the dollar.
The dollar falls to a post World War Two low of 120.45 yen in Tokyo trade. The Bank of Japan intervenes in 1991 -- 1992 to support the yen, selling U.S. dollars.
The Bank of Japan sells yen for much of the year in 1993 to curb its strength.
The dollar fell to a record low against the German mark and a post-war low against the yen in April 1994 -- August 1995. The United States repeatedly intervenes with Japanese and European central banks to prop up the dollar.
The yen has fallen to around 148 to the dollar in August, despite U.S. authorities joining the Bank of Japan to buy yen.
The Bank of Japan sells yen at least 18 times from January 1999 to April 2000, including once via the Federal Reserve and once via the European Central Bank, due to fears that a strong yen will choke off an economic recovery. Sept. 11 -- Bank of Japan intervenes in Japan to sell yen after the Sept. 11 attacks in the United States. The ECB and the New York Federal Reserve operate on behalf of the BOJ.
May-June, 2002 - Bank of Japan intervenes to sell yen, often supported by the Federal Reserve and the European Central Bank. The end of a 15 month campaign to curb the yen's rise is March 2004 -- Japan spends 35 trillion yen, or more than $300 billion, on intervention.
Sept. 15, 2010 - Japan intervenes in the currency market for the first time in a decade, selling yen to stem a rise in the currency after the dollar hit a 15 year low at 82.87 yen.
March 18, 2011 - G 7 nations joined to stem yen strength when the currency spikes to a record high after a massive earthquake, on speculation that Japanese firms would repatriate foreign assets to pay for reconstruction.
Japan intervenes to curb gains that officials fear will derail recovery from an economic slump triggered by the March earthquake and tsunami.