Berlin: After angrily insisting for months that "friends don't spy," the German government struggled on Monday to respond to news media reports that its intelligence services routinely spy on Turkey, a NATO ally, and inadvertently captured at least one conversation each involving Hillary Clinton when she was secretary of state and her successor, John Kerry.

While officials in Berlin sought to downplay the reports, Turkey summoned the German ambassador to demand an immediate investigation and the termination of any espionage activity.

A BND monitoring base in Bad Aibling, near Munich. Credit:AP

"If there is even a bit of truth in these allegations, this is a grave situation that requires an explanation by Germany," Turkey's Foreign Ministry said in a statement.

In a tone of outrage heard repeatedly from politicians in Berlin over the past year when addressing widespread allegations of spying by the US National Security Agency, the Turkish government demanded that German authorities "present an official and satisfactory explanation to the allegations," adding that "if true, these practices should be terminated at once."