Germany announced a series of hardline measures against Turkey yesterday, amid rapidly deteriorating relations between the two Nato partners.
Sigmar Gabriel, the German foreign minister, accused the Turkish government of the "arbitrary" arrest of German citizens on its soil and demanded their immediate release.
In a series of measures that could threaten the fragile Turkish economy, he issued tough new travel advice for Germans visiting the country, and ordered a review of export credit guarantees for German companies investing in Turkey.
He also said Germany would seek a review of €630m of aid Turkey receives each year from the EU, and of Turkey's partial membership of the customs union.
Mr Gabriel described the measures as a complete "realignment" of German policy towards the government of Recep Tayyip Erdogan.
"We expect a return to European values," he said.
"We need our policies towards Turkey to go in a new direction. We can't go on as we are.
"We need to be clearer than we have been, so that those responsible in Ankara understand that such policies are not without consequences."
Angela Merkel, the German chancellor, backed the measures, describing them as "necessary and unavoidable".
The dramatic escalation follows the arrest of Peter Steudtner, a German human rights activist working with Amnesty International, in Turkey.
Mr Gabriel cut short his holiday and returned to Berlin for emergency meetings after the Turkish authorities announced this week that Mr Steudtner was facing terrorism charges.
Turkey earlier rejected an official demand for Mr Steudtner's release, calling it "unacceptable" and accusing Germany of "diplomatic rudeness" and interfering with the Turkish judiciary.
Mr Gabriel yesterday described the allegations against Mr Steudtner as "offensive and absurd".
The human rights campaigner was arrested alongside five other activists at a conference on digital security near Istanbul, together with the local head of Amnesty International.
Turkish media have claimed Mr Steudtner is an MI6 agent and was plotting a coup attempt.
Though the foreign ministry stopped short of advising Germans against all travel to Turkey, it warned that "Germans have been detained in Turkey for reasons that are incomprehensible" and that "consular access has been denied in contravention of international obligations". (© Daily Telegraph London)