A spokesman for Herman Van Rompuy, the president of the European Council, said, "The European Union has demanded and expects full and urgent clarification by the U.S. regarding the allegations."
According to Der Spiegel's report, which it said was partly based on information leaked by Snowden, NSA planted bugs in the EU's diplomatic offices in Washington and infiltrated the building's computer network. Similar measures were taken at the EU's mission to the United Nations in New York, the magazine said.
It also reported that NSA used secure facilities at NATO headquarters in Brussels to dial into telephone maintenance systems that would have allowed it to intercept senior officials' calls and Internet traffic at a key EU office nearby.
As for Snowden, White House national security spokeswoman Caitlin Hayden said the White House won't comment on specific asylum requests but reiterated its message to all countries that he "needs to be expelled back to the U.S. based on the fact that he doesn't have travel documents and the charges pending against him."
Regarding possible effects on U.S. interactions with Russia, she said it remains the case "that we don't want this issue to negatively impact the bilateral relationship."