Spiegel reported in its Saturday online edition that the NSU used bugs, phone taps and cybermonitoring to obtain information from EU institutions in Washington, DC, New York and Brussels.

Edward Snowden, a former NSA contractor who recently leaked classified documents about the monitoring program, provided the documents the magazine cited in its report.

The documents, marked "top secret" and dated September 2010, specifically name the EU as a "target" for surveillance. The NSA appears to have had access to telephone calls, computer documents and emails.

Part of the surveillance included monitoring the Justus Lipsius building in Brussels (pictured above) where the European Council is housed. Every EU member nation has rooms in the building which can be used for phone calls or to access the internet.

Spiegel reports that five years ago, EU security officers had investigated a series of missed calls to NSA offices located in NATO facilities in Brussels.

Snowden fled the United States in May before the initial stories of the NSA's secret phone and data monitoring program were published. The extent of the government monitoring continues to grow as Snowden shares more leaked documents with news outlets.

He is currently believed to be in a transit center at a Moscow airport. The US has called for Snowden's extradition and arrest on espionage charges. He had previously been in Hong Kong, and has submitted an asylum request to the government of Ecuador.

mz/dr (Reuters, dpa)