(CNN) -- European officials reacted with fury Sunday after a report that the U.S. National Security Agency spied on EU offices.
The European Union warned that if the report is accurate, it will have tremendous repercussions.
"I am deeply worried and shocked about the allegations," European Parliament President Martin Schulz said in a statement. "If the allegations prove to be true, it would be an extremely serious matter which will have a severe impact on EU-US relations. On behalf of the European Parliament, I demand full clarification and require further information speedily from the U.S. authorities with regard to these allegations."
German Justice Minister Sabine Leutheusser-Schnarrenberger "said if the accusations were true it was reminiscent of the Cold War," ministry spokesman Anders Mertzlufft said, adding that the minister "has asked for an immediate explanation from the United States."
The German newspaper Der Spiegel reported that "the U.S. placed bugs in the EU representation in Washington and infiltrated its computer network. Cyberattacks were also perpetrated against Brussels in New York and Washington."
The information came from secret documents obtained by Edward Snowden, which the paper "has in part seen," according to the report. "A 'top secret' 2010 document describes how the secret service attacked the EU's diplomatic representation in Washington."
Ben Rhodes, White House deputy national security adviser for strategic communications, said he had not seen the report and "would not comment on unauthorized disclosures of intelligence programs. The intelligence community would be the most appropriate to do that."
Rhodes added that "those are some of our closest intelligence partners, so it's worth noting that the Europeans work very closely with us. We have very close intelligence relationships with them."
U.S. intelligence officials have not responded immediately to the report.
European Union spokeswoman Marlene Holzner, in a e-mail to CNN, said, "We have immediately been in contact with the U.S. authorities in Washington DC and in Brussels and have confronted them with the press reports. They have told us they are checking on the accuracy of the information released yesterday and will come back to us."
Snowden, who has acknowledged leaking classified documents, is in Russia and seeking asylum in Ecuador.
U.S. Vice President Joe Biden asked Ecuador "to please reject" the request for asylum, according to Ecuadorian President Rafael Correa.
Russian President Vladimir Putin has said, "The sooner he selects his final destination point, the better both for us and for himself."
A top Russian lawmaker said Sunday that Russia must not hand Snowden over to the United States.
"It's not a matter of Snowden's usefulness to Russia, it's a matter of principle," Alexei Pushkov -- who heads the international affairs committee at the Duma, the lower house of parliament -- said on Twitter.
"He is a political refugee and handing him over is morally unacceptable," he said.
CNN's Susanna Palk contributed to this report.
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