Investors were digesting a block of bad news about the euro zone crisis. Following Fitch Ratings cut of Greece's debt ratings by three notches on Friday, pushing the country's debt deeper into junk status, rival Standard & Poor's cut its outlook for Italy to "negative" from "stable" on May 21.

Spanish voters added to the angst, becoming the latest electorate to punish sitting European governments for the current economic climate.

The ruling Socialists were hit by stinging losses in local elections and now face a balancing act between voter anger over sky-high unemployment and investor demands for strict austerity measures.

Investors reacted to the various events with a burst of risk aversion, shifting funds into US government debt, gold and the dollar.

The euro fell, for example, to a record low against the generally safe-haven Swiss franc.

It lost around 1 percent against the dollar and was down 1.2 percent against the yen.

Worries about some form of debt restructuring by Greece was a key element of the sell off.