European leaders expressed outrage Sunday at leaked reports that the U.S. government bugged the offices of their European Union delegates, with some calling for the suspension of ongoing talks.

U.S. documents reportedly leaked by former intelligence employee Edward Snowden indicate the National Security Agency bugged EU offices in Brussels, New York and Washington. A spokesman for German Chancellor Angela Merkel said Monday she was alienated by the reports and demands "trust restored" with the U.S.

U.S. Secretary of State John Kerry said such taps are in line with the international affairs between countries that undertake numerous activities to protect their national interests. He did not know the particulars of this program and said he would look into it.

Ongoing negotiations for a new trans-Atlantic trade treaty could be sunk over the accusations, say officials from France, Germany, Italy, Luxembourg and the EU government itself.

"The monitoring of friends – this is not acceptable, it can't be tolerated," said Merkel, according to German magazine Der Spiegel. "We're no longer in the Cold War."

"Our cooperation must be based on trust. This trust must be reestablished now," she said.

The leaked documents indicate Germany was one of the most highly targeted countries in the program, reports Der Spiegel, which first published the content of the leaked documents.

Snowden remains in a Russian airport, where WikiLeaks Founder Julian Assange says he is marooned. WikiLeaks has helped the former intelligence analyst leak these materials. Snowden was originally bound for Ecuador, though that country has distanced itself from initial reports that it would grant him asylum, pointing instead to Russia to make the next decision on his fate.

The initial round of leaked documents unveiled secretive government programs that gather metadata on phone calls and internet access within the U.S., including for those who have not committed crimes. NSA officials claim the data is only used to find connections with known terrorists, and does not allow actual phone or computer taps without a warrant.

Former NSA Director Michael Hayden said Sunday that U.S. intelligence services should release more information about its surveillance programs to assuage growing anxiety among the American people.

Americans would be more comfortable with the monitoring programs if they knew more about how they were conducted, Hayden said on CBS's "Face the Nation."