Investors also continued to seek the safety of United States Treasury bonds, as yields on 10-year bonds briefly touched 1.90 percent, the lowest ever, before closing at 1.98 percent.

Adding to the anxiety, several immediate challenges face European officials as they try to calm markets worried about the debt crisis spreading.

In the coming weeks, the 17 countries of the euro currency zone each could agree to a July deal brokered to bail out Greece again and possibly the region’s ailing banks. Along with getting unanimity, more immediate obstacles could trip up the agreement.

On Wednesday, Germany’s top court upheld the legality of Berlin’s rescue packages, but said any future bailouts for debt-stricken euro zone countries must be approved by a parliamentary panel. On Thursday, officials in Finland are to express their conditions for approving the deal, and other countries may follow with their own demands to ensure their loans will be paid back.

Though they have not succeeded in calming the markets, European leaders have taken a series of steps to avert a Lehman-like failure. New credit lines have been opened by the European Central Bank for institutions that need funds, while the proposed Greek bailout would provide loans to countries that need to recapitalize their banks. In addition, the central bank has been buying up bonds from Italy and Spain, among other countries, to keep interest rates from spiking. Many of these have been bought from European banks, effectively allowing them to shed troubled assets for cash.

While the problems in smaller countries like Greece and Ireland are not new, in recent weeks the concerns have spread to banking giants in countries like Germany and France that are crucial to the functioning of the global financial system and are closely linked with their American counterparts. What is more, worries have surfaced about the outlook for Italy, whose debt dwarfs that of other smaller troubled borrowers like Greece.

Image “This crisis has the potential to be a lot worse than Lehman Brothers,” said George Soros, the hedge fund investor, citing the lack of a pan-European body to handle an extreme banking crisis. Credit... Left, Jorge Silva/Reuters; Tom White for the New York Times

“It seems like the banking sector globally is being hurt on multiple fronts,” said Philip Finch, a bank strategist with UBS in London. “It’s definitely getting worse.”