A video from Spiegel Online Shows NSA has 80 SCS sites worldwide, including in big cities such as Beijing, Shanghai and Hong Kong. (Photo: haiwainet. cn)

US intelligence has been operating a global network of 80 Special Collection Services (SCS), including Asia listening posts in cities such as Beijing, Shanghai, Chengdu, Hong Kong and Taipei, the German magazine Spiegel reports.

In an SCS document cited by the magazine, the agency said it had a "not legally registered spying branch" in the US embassy in Berlin, the exposure of which would lead to "grave damage for the relations of the United States to another government".

Spiegel also reported that the telephone number of Angela Merkel, the German chancellor, has been a target of US surveillance since 2002, and was still under surveillance until weeks before before President Barack Obama visited Berlin in June.

Defending the NSA's actions, the US administration has insisted that it is necessary to intercept vast amounts of electronic data to effectively fight terrorism, but the White House has said it is examining the concerns of other countries as part of an ongoing review of how the US gathers intelligence.