BERLIN - The U.S. National Security Agency and its British counterpart GCHQ gained secret access to the networks of German Web providers including Deutsche Telekom AG as it sought to peer into computers all over the world, according to a e-mails from the German magazine Der Spiegel, citing documents provided by fugitive NSA employee Edward Snowden.

The agencies conducted an operation called "Treasure Map," which sought close to real-time access to individual routers as well as computers, smartphones and tablets connected to the Internet, Spiegel reported Saturday in an e-mailed preview of an article to be published on Sept. 15.

The New York Times reported the existence of Treasure Map last year.

Deutsche Telekom said it is investigating the allegations and hasn't found evidence of manipulation or external access to its networks. The company, in an e-mailed statement, said it has informed German authorities and is reviewing its networks with external information-technology experts.

Access by foreign security agencies would be "completely unacceptable," the Bonn-based company said in its statement.

Deutsche Telekom and Cologne, Germany-based Netcologne were marked on a leaked graphic with red dots, indicating surveillance access points, Spiegel reported. Netcologne didn't immediately respond to a phone call seeking comment today.

A spokeswoman for the NSA declined to comment on "any alleged, specific foreign intelligence activities." In an e-mailed statement Saturday, Vanee Vines said the agency "collects only those communications that we are authorized by law to collect for valid foreign intelligence and counterintelligence purposes."