(CNN) -- President Barack Obama responded to outrage by European leaders over revelations of alleged U.S. spying on them by saying Monday that all nations, including those expressing the strongest protests, collect intelligence on each other.

The German news magazine Der Spiegel reported Sunday that classified leaks by former National Security Agency contractor Edward Snowden detailed NSA bugging of European Union offices in Washington and New York, as well as an "electronic eavesdropping operation" that tapped into an EU building in Brussels.

Mounting anger throughout Europe on Monday included a threat by French President Francois Hollande to halt talks with the United States on trade and other issues unless the bugging stopped.

U.S. and EU officials are scheduled to begin talks on a proposed trans-Atlantic free trade agreement next week.

The European Commission will sweep its offices for electronic listening devices and other security breaches, a spokeswoman said Monday.

Asked at a news conference in Tanzania about the latest leaks involving Snowden, Obama said he needed more information on the specific programs cited in the Der Spiegel report, but made clear such spying was commonplace.

"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 should I end up meeting with their leaders," Obama said. "That is how intelligence services operate."

Meanwhile, Russian President Vladimir Putin opened the door on Monday to Snowden possibly staying in Russia. The admitted NSA leaker has been in the international transit lounge of the Moscow airport seeking asylum in Ecuador.

Snowden "must stop his work aimed at harming our American partners" if he wants to stay in Russia, Putin said. Previously, Putin had said Snowden should depart the airport for his final destination, wherever it might be.

Conflicting reports emerged Monday that Snowden was seeking asylum in Russia.

Obama said Monday that 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.

The president confirmed that the United States and Russia have had "high-level" discussions about Snowden, after an earlier report from Russia that the two nations' top law enforcement officials were working together to resolve the situation.

The new bugging controversy follows earlier European discontent over revelations of U.S. surveillance of overseas e-mails related to terrorism, as well as the collection of phone records as a database for further court-approved investigation.

Obama sought to distinguish between what he portrayed as normal intelligence-gathering and the specific anti-terrorism programs disclosed by Snowden's earlier leaks to The Guardian newspaper in London and the Washington Post.

In the end, he said, U.S. and European allies "work so closely together that there is almost no information that is not shared between our various countries."

Hollande, however, said bugging of EU offices went beyond the anti-terrorism programs previously revealed and 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.

Der Spiegel reported the allegations Sunday, citing information from secret documents obtained by 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.

To Michael Hayden, a former director of the NSA and CIA, the report reflected the reality of international spying.

"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," he told CBS on Sunday.

Obama declined to comment in-depth on the Der Spiegel article, saying his staff needs to analyze the report to figure out which, if any, U.S. surveillance programs it involved.

"When we have an answer we will make sure to provide all the information that our allies want in what exactly the allegations have been," he said.

Describing himself as "the end user of this kind of intelligence," Obama said he telephones Hollande or German Chancellor Angela Merkel or British Prime Minister David Cameron if he wants to know what they're thinking.

"Ultimately, you know, we work so closely together that there is almost no information that is not shared between our various countries," Obama said.

Reactions abroad

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.

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," Seibert said. "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," while European Parliament President Martin Schulz said Sunday 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.

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

The U.S. Director of National Intelligence's office 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 DNI 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."

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 faces espionage charges in the United States and was seeking asylum from Ecuador.

Vice President Joe Biden asked Ecuador "to please reject" the request for asylum, according to Ecuadorian President Rafael Correa.

Snowden and his asylum bid

On Saturday night, Correa said the ball was in Russia's court.

"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."

CNN's Barbara Starr, Miriam Falco, Kathryn Tancos, Alexander Hunter, Claudia Rebaza, Patrick Oppmann, Josh Levs, Catherine Shoichet and Susanna Palk contributed to this report.

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