ROME — Russia denied reports in the Italian news media and elsewhere on Wednesday that Russian spy agencies distributed special USB thumb drives doctored to let them eavesdrop on delegations attending last month’s Group of 20 summit meeting in St. Petersburg.

“We don’t know the sources of the information,” said Dmitri S. Peskov, the spokesman for President Vladimir V. Putin of Russia, according to RIA Novosti, the state news agency. “However, this is undoubtedly nothing but an attempt to shift the focus from issues that truly exist in relations between European capitals and Washington to unsubstantiated, nonexistent issues.”

European leaders have been outraged by reports that the National Security Agency spied on allies in Europe, including Chancellor Angela Merkel of Germany. The American spying operation has created a diplomatic crisis for the Obama administration, stirring fury in France, Spain and Germany, while intensifying criticism in Washington about the scope and methods of American espionage.

On Wednesday, the focus shifted to Russia, as Corriere della Sera, a leading Italian newspaper, published allegations that the Group of 20 meeting was the scene of a major effort in Russian espionage. According to the paper, Herman Van Rompuy, president of the European Council, had a debriefing with security officials after returning from St. Petersburg. The report was swiftly picked up by news agencies and newspapers in other countries.