The euro briefly rose to a record high versus the dollar for the fifth session running on Wednesday and tested last year's lifetime high against the yen as investors' bearish views of the U.S. currency dominated trading.
There was little news to turn investors' focus away from their worries about the burden of the U.S. current account deficit on the dollar and about the ability of the U.S. economy to attract enough money to plug this shortfall.
Trading volumes were also thin in the holiday period between Christmas and New Year.
"The euro has been strong for a few days now. It is a repeat of late-2002 and late-2003," said Trevor Dinmore, foreign exchange strategist at Deutsche Bank in London.
"When you have low liquidity at the end of the year, you have fewer flows and you see more dollar weakness."
The euro hit a record high of $1.3646 before paring its gains to trade at $1.3606 at 1300 GMT.
It also strengthened against the British pound to reach its highest level in more than one year at 70.89 pence.
Against the yen, the euro traded at 140.80 yen, just below last year's record high around 140.90 yen.
The Swiss franc briefly lost some ground after Switzerland's leading KOF indicator fell much more than expected in December, hitting 0.49 which compared with expectations for a 0.68 reading.
The franc moved away from levels near this month's nine-year high against the dollar. It traded at 1.1332 francs per dollar, compared with 1.1294 in early December.