The United States taps 500 million phone calls, e-mails and text messages in Germany in a typical month and has classed its biggest European ally as a target similar to China, according to secret US documents quoted by a German newsmagazine.

Exposing the latest details in a string of reputed spying programs, Der Spiegel quoted from an internal NSA document that it said its reporters had seen.

The document Der Spiegel cited showed that the US categorized Germany as a "third-class" partner and that surveillance there was stronger than in any other EU country, similar in extent to China, Iraq or Saudi-Arabia.

"We can attack the signals of most foreign third-class partners, and we do it, too," Der Spiegel quoted a passage in the NSA document as saying.

It said the document showed that the NSA monitored phone calls, text messages, e-mails and Internet chat contributions and has saved the metadata - that is, the connections, not the content - at its headquarters.

On an average day, the NSA monitored about 20 million German phone connections and 10 million Internet data sets, rising to 60 million phone connections on busy days, the report said.

While it had been known from disclosures by Snowden that the US tapped data in Germany, the extent was previously unclear.

Reuters