The alleged U.S. spying on German Chancellor Angela Merkel's mobile phone may have been run out of its Berlin embassy, less than a kilometer (mile) from the chancellery, media reported Friday.

The surveillance was allegedly conducted by a listening post of the Special Collection Service, run jointly by the National Security Agency (NSA) and the Central Intelligence Agency, said the Sueddeutsche Zeitung.

The eavesdropping program "works worldwide in American embassies and consulates, mostly in secret," it said, citing documents provided by fugitive former NSA intelligence contractor Edward Snowden.

The alleged spying on Merkel, made public Wednesday by the German government, sent shock waves though the country and was roundly condemned by legislators and in the media.

"Spying between friends, that's just not done," Merkel said Thursday from Brussels, where the agenda of a European Union summit was hijacked by the growing spy scandal.