(CNN) - The European Commission will sweep its offices for electronic listening devices and other security breaches following revelations of alleged U.S. surveillance programs targeting European leaders, a commission spokeswoman said Monday.
The allegations, reported Sunday by the German news magazine Der Spiegel, threaten to derail negotiations on a variety of issues with the United States, French President Francois Hollande said Monday. U.S. and EU officials are scheduled to begin talks on a proposed trans-Atlantic free trade agreement next week.
Hollande said any such surveillance must stop immediately before negotiations can go forward.
"We know that there are systems which have to control notably for the threat against terrorism, but I do not think that this is in our embassies or in the EU that this risks exist," he said.
Hollande's comments and the planned security sweep come amid building outrage in Europe over allegations that the National Security Agency had bugged EU offices in Washington and New York and conducted an "electronic eavesdropping operation" that tapped into an EU building in Brussels, Belgium.
However, some analysts said such is common, even among allies.
Michael Hayden, a former director of the NSA and CIA, told "Face the Nation" on CBS on Sunday morning that "any European who wants to go out and rend their garments with regard to international espionage should look first and find out what their governments are doing."
Der Spiegel reported the allegations Sunday, citing information from secret documents obtained by self-avowed NSA leaker Edward Snowden and "in part seen" by the news magazine.
In Brussels, Der Spiegel says, the agency targeted the Justus Lipsius Building, which houses the European Council and the EU Council of Ministers, the union's main decision-making and legislative body.
And in Washington, the magazine report claims, the NSA installed bugs in the European Union's building and infiltrated its computer network.
President Barack Obama, traveling in Africa, declined to comment in-depth on the article, saying his staff needs to analyze the report to figure out which, if any, U.S. surveillance programs it pertains to.
But he said all intelligence services need to gather information from sources that aren't readily available through public sources.
"I guarantee you that in European capitals, there are people who are interested in if not what I had for breakfast, at least what my talking points might be if I end up meeting with their leaders," he said.
He also said most information gathered by U.S. officials is shared with European allies.
Also on Monday, Obama said Snowden had traveled to Russia without a valid passport or legal papers, and he hoped that Moscow would handle the case as it would any other travel-related matter. Obama confirmed that the United States and Russia have had "high-level" discussions about Snowden.
The reports elicited particular outrage in Germany, where Der Spiegel reported that NSA spying had targeted telephone and Internet connection data in Germany more than any other European nation.
Citing the Snowden documents, the news magazine reported that an average of up to 20 million phone connections and 10 million Internet data connections are surveyed daily. Der Spiegel noted that the intensity of surveillance puts the U.S. ally on par with China, Iraq and Saudi Arabia.
German Chancellor Angela Merkel's spokesman Steffan Seibert cautioned Monday against taking the report as fact without further confirmation.
"If it is, though, confirmed that diplomatic representations of the EU and some European countries were spied upon, we have to say clearly: The bugging of friends is unacceptable. That cannot happen at all. We are no longer in the Cold War."
The German and French foreign ministries planned to meet with the U.S. ambassadors to those countries to talk about the allegations.
The Italian Foreign Ministry called the reports "a very thorny affair."
On Sunday, European Parliament President Martin Schulz said he was "deeply worried and shocked" by the claims.
"If the allegations prove to be true, it would be an extremely serious matter which will have a severe impact on EU-U.S. relations," he said. "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."
French Foreign Minister Laurent Fabius called for a swift explanation from American authorities.
"These acts, if they are confirmed, would be absolutely unacceptable," he said in a statement.
Another report Sunday claimed that surveillance extended beyond European offices.
The Guardian newspaper reported that one NSA document leaked by Snowden describes 38 embassies and missions as "targets" and details surveillance methods that include planting bugs in communications equipment and collecting transmissions with specialized antennae.
Targets included France, Italy, Greece, Japan, Mexico, South Korea, India and Turkey, according to The Guardian.
CNN has not independently confirmed the allegations in the reports from Der Spiegel and The Guardian.
What the U.S. has to say
U.S. officials did not immediately respond to The Guardian's report. The Office of the Director of National Intelligence declined to comment Sunday on specific allegations published in Der Spiegel.
"The United States government will respond appropriately to the European Union through our diplomatic channels, and through the EU/U.S. experts' dialogue on intelligence that the U.S. proposed several weeks ago," the office said in a statement. "We will also discuss these issues bilaterally with EU member states. While we are not going to comment publicly on specific alleged intelligence activities, as a matter of policy, we have made clear that the United States gathers foreign intelligence of the type gathered by all nations."
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."
Snowden and his asylum bid
Snowden has revealed himself as the source of documents outlining a massive effort by the NSA to track cell phone calls and monitor the e-mail and Internet traffic of virtually all Americans.
Now Snowden, who faces espionage charges in the United States, is in Russia and seeking asylum from Ecuador.
U.S. Vice President Joe Biden asked Ecuador "to please reject" the request for asylum, according to Ecuadorian President Rafael Correa.
WikiLeaks founder Julian Assange, whose organization facilitates the release of classified documents and is assisting Snowden's asylum bid, said he couldn't reveal details about the former NSA contractor's specific location or the status of his case. He criticized U.S. officials for pressuring Ecuador on the matter.
"Asylum is a right that we all have. It's an international right. The United States has been founded largely on accepting political refugees from other countries and has prospered by it. Mr. Snowden has that right," said Assange. "Ideally, he should be able to return to the United States. Unfortunately, that's not the world that we live in, and hopefully another country will give him the justice that he deserves."
Former Cuban leader Fidel Castro weighed in Sunday. In a letter to Nicaraguan President Daniel Ortega published in Cuban state media, Castro praised Ecuador's president for standing up to U.S. threats over Snowden.
On Saturday night, Correa said the ball was in Russia's court.
"We didn't ask to be in this situation. Mr. Snowden has been in touch with Mr. Assange, who recommended he ask for asylum in Ecuador. In order to process this request, he needs to be in Ecuadorian territory," Correa said in an interview with Ecuador's Oromar TV on Saturday night. "At this point, the solution for Snowden's final destination is in the hands of the Russian authorities."
While Russian President Vladimir Putin has said Snowden is a free man and urged him to decide where he is going, quickly, 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.