The yen was volatile on speculation the Bank of Japan was concerned about the Japanese currency's strength.
The Chinese currency has hit a year-to-date high against the dollar, leaving experts contemplating whether officials will step in to devalue the yuan.
The dollar fell sharply against major currencies after the Federal Reserve kept interest rates.
The dollar fell sharply against the yen as weak U.S. retail sales data compounded investors' search for safety.
Currency markets were off to a relatively quiet start on Monday, stabilizing after last week's wild swings.
The dollar was higher, after nearing a one-month low against a basket of major currencies.
As investors digested the ECB's new stimulus package, some are suggesting Draghi has shelved plans to drive the euro lower for the time being.
The euro rose to a three week-high against the dollar on Thursday, rallying from a six-week low.
The euro held firm on Wednesday in choppy trading as investors awaited an European Central Bank meeting.
Weak Chinese trade data stoked safe-haven demand for the yen on Tuesday.
The dollar index fell as big gains in oil prices rekindled demand for the euro and commodity-sensitive currencies.
The dollar hit one-week lows against the euro and fell against the yen after a drop in U.S. wages in February overshadowed strong jobs growth.
The U.S. dollar was set to post its biggest one-day percentage decline against the euro in more than three weeks.
The U.S. dollar dipped against the yen on Wednesday on concerns over U.S. economic growth but hit a more than one-month high against the euro.
The U.S. dollar rebounded against the yen and hit one-month highs against the euro on Tuesday.
The yen rose broadly on Monday as investors sought its safety following a statement from the Group of 20 countries.
The dollar gained after generally upbeat U.S. data revived some expectations that the Fed could consider raising interest rates again this year.
Gains in European stocks helped sterling and the dollar climb against safe-haven currencies like the yen on Thursday.
Sterling tumbled to a seven-year low on Wednesday on heightened fears of a possible British exit from the European Union.
The yen and Swiss franc rallied across the board on Tuesday as a recent rebound in stocks and crude oil faded.