Euro fell sharply on Thursday versus the US currency, hitting a three-week low and dropping below its 100-day moving average for the first time since February.
Rate still vulnerable to worries that Greece's debt crisis may be getting out of control, as a new bailout scheme to keep Greece from defaulting remained elusive while Greek protests against austerity turned violent in Athens.
"Investors are getting worried that policymakers can't agree on measures for Greece. Even though the Greek economy accounts for only a small part of the euro zone economy, it could affect the whole European financial system if it is considered to be in default," said Kimihiko Tomita, forex manager at State Street.

The dollar also held firm against safe-haven currencies like the Swiss franc and yen.
For the Swiss franc, the focus was on the Swiss National Bank, which kept rates on hold at 0.25% as expected. Analysts expect the bank to raise rates by 25 basis points in September and again in December.
Commodity currencies like the Australian dollar also lost ground to the U.S. dollar, though they fared better elsewhere.
Even hawkish comments from the Reserve Bank of Australia on Wednesday provided little support for the Aussie dollar.