BERLIN - The US National Security Agency ( NSA) not only monitors the communication of European citizens, but also has an eavesdropping program targeting the European Union (EU) offices, German magazine Der Spiegel reported Saturday.

The magazine cited confidential documents it was partly able to obtain from US whistleblower Edward Snowden. The former CIA agent fled to Hong Kong last month and revealed a NSA-operated classified surveillance project code-named PRISM, which can trace worldwide e-mails and phone calls.

A document dated September 2010 and classified as "strictly confidential" showed how the NSA spied the EU's diplomatic mission in Washington, it said.

Eavesdropping bugs were installed in the EU buildings and the internal computer network was infiltrated, through which the American intelligence can get access to EU meetings, e-mails and internal documents, it added.

The EU representation at the United Nations in New York was also under similar surveillance, the magazine said.

In addition, the US intelligence also keeps regular eavesdropping and monitoring of the Justus Lipsius building, the headquarters of the Council of the European Union, it said.

The classified phone and internet surveillance program, disclosed by The Guardian and The Washington Post, has sparked an outcry in Europe over concerns about intrusion into the privacy of individuals.

The EU has warned the Obama Administration of "grave adverse consequences" to the rights of the European citizens from the spy scheme and demanded "swift and concrete" answers.

The US intelligence scandal has also stirred massive controversies in the country about the balance between privacy and national security.

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