Members of the CIA and the National Security Agency (NSA) used diplomatic cover to collect information from the camouflaged listening post in Geneva and on the roofs of a dozen other American embassies in Europe, the magazine said.
The spying, conducted by a combined “Special Collection Service” also tapped into radio and satellite communications, the publication said.
It based its information on a 2010 document, made public by Edward Snowden, the former NSA consultant and whistleblower who recently sought refuge in Russia.
The document describes the Geneva listening post as one of 80 across Europe.
The information comes as European politicians reacted angrily to increasing evidence of American spying on foreign leaders, even to the point of tapping German Chancellor Angela Merkel’s mobile phone.
Computer specialist Snowden disclosed back in June that he worked for the CIA as a technical assistant in Geneva in 2007 before being assigned two years later to work for the NSA as an employee of defence contractor Booz Allen Hamilton.
He told The Guardian newspaper of an incident in which CIA agents got a Geneva banker drunk in order to recruit him to provide inside information about the Swiss banking industry.
Geneva-based American political scientist Daniel Warner told the Swiss daily Tages Anzeiger that Der Spiegel’s revelations were “plausible”.
He recalled that the CIA has been active in Switzerland since the end of the Second World War.
Swiss politicians interviewed by Tages Anzeiger also thought the information relayed by Der Spiegel from Snowden was credible and precise.
Carlo Sommaruga, a Socialist federal MP from Geneva, said the Swiss intelligence service should develop counter-espionage so that a parliamentary commission can have detailed idea of the extent of the problem in international Geneva.
Meanwhile, NSA chief Keith Alexander attempted to downplay the the activities of his organization, telling an intelligence committee hearing in Washington on Tuesday that reports of the NSA collecting millions of phone calls were “absolutely false”.
“And it is false that it was collected on European citizens.”
Alexander maintained that information on European citizens was provided to the NSA by European intelligence agencies, who have their own surveillance programmes
NSA officials reminded politicians that their goal is to collect information to thwart terrorism plots, using means that were enhanced in the wake of the 9-11 terrorist attacks on the US.