German Ambassador in Moscow Alexander Graf Lambsdorff was summoned to the Russian Foreign Ministry on Monday, a source told Sputnik.
"The German ambassador was summoned to the [Russian] Foreign Ministry today," the source said.
A conversation between senior German military officers on security topics concerning Russia and Ukraine was published by Russian media on Friday. Later, German news agency DPA reported that the tape was authentic.
German Defense Minister Boris Pistorius said, in turn, expressed hope that the first results of an investigation into the audio recording will be ready early next week.