The dollar dropped to its lowest in four weeks against the yen on Monday as last week's soft U.S. jobs data dampened optimism about the outlook for the world's largest economy and fueled uncertainty as to the pace of the Federal Reserve's reduction in stimulus.
The dollar's weakness also helped push the Australian dollar to a one-month high and the New Zealand dollar to an 8-week high against the greenback.
(Read more: Contrarian call: US dollar to weaken further in 2014)
In early New York trading, the dollar slid nearly 1 percent against the yen to 103.33 yen, after earlier falling to 102.97, its lowest level since Dec. 18. Dollar/yen was one of the strongest-performing major currency pairs last year and many hedge funds have been betting the trend will continue as the Fed cuts back its huge bond-buying program even as the Bank of Japan continues to provide even more stimulus this year.
But many traders were taken by surprise by the U.S. non-farm payrolls data, which showed a rise of 74,000, well short of the 196,000 analysts had expected.
(Read more: Dollar falls broadly on weak US jobs data)
Yields on 10-year U.S. Treasuries, which were above 3 percent in the middle of last week, have fallen to around 2.85 percent, their lowest since mid-December, lending less support to the dollar.
The implied yields on Fed funds futures also tumbled as markets pushed back the timing of the first interest rate hike out towards late-2015 from mid-2015. Investors were also looking for direction with Japanese financial markets closed on Monday for a public holiday.
Dollar selling against major currencies was driven by computer portfolios, according to one London-based trader.
The yen also pushed higher versus the euro, which fell nearly 1 percent to 141.05 yen. The euro touched a low of 140.48 yen, its lowest level in six weeks.
The euro was down slightly against the dollar at $1.3649, staying above a one-month trough of $1.3548 hit on Thursday.
(Read more: Could currency wars make a comeback in 2014?)
Volumes were high in the Australian dollar, which has been weak against the U.S. dollar in recent months after comments by the central bank governor saying he would prefer to see the local dollar lower. The Aussie hit a one-month high of US$0.9077 and was last at US$0.9054, up 0.6 percent.
The New Zealand dollar touched an eight-week high of US$0.8387, and was last at US$0.8356, up 0.7 percent.
The Canadian dollar headed back towards its lowest in more than four years against the greenback after data showed the country unexpectedly shed jobs last month. The loonie, which fell in every session last week against its U.S. peer, last stood at C$1.0869 per dollar. The U.S. dollar had scaled a peak of C$1.0944 on Friday, the greenback's strongest level since October 2009.