A?snapshot of the Der?Spielgel report on U.S. spying on EU.

The foreign policy chief of the European Union (EU) Catherine Ashton said on Sunday that the EU has requested the U.S. to give an explanation for the 'bugging' reports.

"The European Union is aware of the press reports, alleging that EU premises have been under surveillance," said Ashton in her statement, "As soon as we saw these reports, the European External Action Service made contact with the US authorities in both Washington DC and Brussels to seek urgent clarification of the veracity of and facts surrounding these allegations."

"The US authorities have told us they are checking on the accuracy of the information released yesterday and will come back to us as soon as possible," she said, "While this is clearly a matter for concern, we will make no further comments at this stage, until we have more clarity on the matter."

The German news magazine?Der Speigel?reported on Sunday that the National Security Administration of the U.S. conducted not only online surveillance of European citizens, but also appears to have specifically targeted buildings housing European Union institutions.

Citing?documents obtained?from Snowden, the report described how the National Security Agency?monitored EU's Washington and New York offices and conducted an "electronic eavesdropping operation" that tapped into a EU building in Brussels, Belgium.