German prosecutors are investigating allegations that U.S. intelligence agencies conducted a massive spying program in Germany in the wake of revelations by the weekly Der Spiegel that up to 500 million telephone and online communications were intercepted monthly.

Prosecutors are looking at whether the National Security Agency, or NSA, violated German privacy laws by obtaining, analyzing and warehousing the personal information of German citizens, Der Spiegel reported.

The NSA considered Germany a "priority target" for its surveillance operations, with the program monitoring the communications of the government and Chancellor Angela Merkel's office, the magazine said.

Documents leaked by former NSA contractor Edward Snowden shed light on the systematic surveillance program targeting Germany, Der Spiegel said.

The NSA monitored about 20 million telephone conversations and 13 million Internet communications on an average day, Der Spiegel said.

The low was 13 million communications intercepts on Christmas Eve 2012 and the high was 60 million intercepts on Jan. 7, the news magazine said. EFE