Germany's Spiegel weekly: It was spied on by US intelligence

German news weekly Der Spiegel charged Friday that it was spied on by US secret services and said it had filed a criminal complaint with the country's chief prosecutor.

The Hamburg-based magazine has taken a leading role in reporting the disclosures of fugitive US intelligence contractor Edward Snowden on mass surveillance by the US National Security Agency (NSA).

The case dates back to mid-2011 and predates the flight of Snowden and his NSA leaks, Der Spiegel reported online and in its magazine issue to be published Saturday.

It said the US Central Intelligence Agency (CIA) had warned Chancellor Angela Merkel's top spy services coordinator, Guenter Heiss, of a source Der Spiegel allegedly had inside the German government.

The magazine said the alleged contact was transferred soon afterwards, to a position to research the history of Germany's BND intelligence agency.

Der Spiegel said the official reason given was to cut costs, and the Merkel government had kept quiet about the case to a parliamentary intelligence oversight panel that sits behind closed doors.

"The Spiegel assumes it was bugged by US intelligence," the magazine said in a statement.

"It has therefore filed a criminal complaint Friday with the Federal Prosecutor in Karlsruhe on suspicion of secret service activity and breach of the secrecy of telecommunications."

It was Der Spiegel that first reported in 2013 of the NSA's alleged tapping of Merkel's cellphone, which amid the wider NSA scandal badly strained transatlantic relations.