BRUSSELS  European officials told Greece on Tuesday that it must immediately explain how the government used complex financial tactics engineered by Wall Street to mask its rising debt, and warned that they might widen their inquiry to other countries that use the euro.

Finance ministers gathered here also gave Greece one month to prove it could cut its deficit this year to 8.7 percent of the nation’s economic output, from 12.7 percent. If a review finds that Greece’s blueprint for deficit reduction is too weak, officials will demand deeper spending cuts.

Greece’s huge public deficit and high debt levels have prompted a crisis of confidence in the financial markets, and the European single currency is facing its biggest test since its inception.

Meanwhile, Greek civil servants took to the streets on Tuesday to protest government austerity measures. Customs inspectors, tax collectors, trade unions and other unions have gone on strike in recent weeks, and each new wave of strikes appears to be more strident. On Tuesday, a bomb exploded at JPMorgan Chase’s offices in Athens, The Associated Press reported. No one was injured.