“The Turkish government needs to immediately and directly hear the German government's outrage and incomprehension as well as its crystal-clear expectations in the case of Peter Steudtner, and this time without diplomatic niceties,” foreign ministry spokesman Martin Schaefer said.
He said the envoy was told “in no uncertain terms” that the detention of Steudtner and five other activists including Amnesty International's Turkey director was “incomprehensible and also unacceptable”.
Berlin demanded Steudtner's “immediate release” as well as consular access.
“The Turkish government representative said he would deliver this message immediately” to Ankara.
A Turkish court on Tuesday ordered six human rights activists including Amnesty International's Turkey director remain in custody for allegedly aiding a “terror” group, a charge Schaefer branded “absurd”.
Chancellor Angela Merkel has slammed the detention of the six activists as “unjustified” and pledged to “advocate for (Steudtner) on all levels”.
Schaefer added that German Foreign Minister Sigmar Gabriel would interrupt his summer holidays and return to Berlin over the “dramatic escalation in Turkish actions” to determine which “further measures” could be taken.
Relations between Turkey and Germany, home to three million ethnic Turks, have been badly strained, particularly since the failed coup attempt a year ago against Turkish President Recep Tayyip Erdogan.
Berlin has voiced deep concerns over mass arrests and sackings of alleged coup plotters since, and a host of other civil rights controversies.
One dispute centres on Deniz Yucel, a German-Turkish journalist with the Berlin-based newspaper Die Welt who was imprisoned by Turkey on terror charges earlier this year.