Germany on Thursday vowed stinging measures impacting tourism and investment in Turkey and a full  “overhaul” of their troubled relations, signaling its patience has snapped after Ankara’s arrest of a German human rights activist.

The foreign ministry stepped up its travel advisory for Turkey, warning it could no longer guarantee its citizens’ safety amid “arbitrary” mass arrests, a step set to impact Turkey’s crucial tourism sector.

Foreign Minister Sigmar Gabriel, a day after summoning Turkey’s ambassador, returned from holidays to Berlin to deliver his unusually strong comments towards President Recep Tayyip Erdogan.

Relations between Turkey and Germany have been badly strained, particularly since the failed coup attempt a year ago against Erdogan.

Gabriel said Germany would review state guarantees for foreign investment in Turkey and urge businesses against putting their money there, and also review its support for EU financial flows to the long-time aspirant to membership of the bloc.

He accused Erdogan of trying to muzzle “every critical voice” with mass arrests in sweeping crackdowns since the failed coup against him in July 2016.

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 centers 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.

Gabriel stressed that Germany still wanted to rebuild relations with its long-time ally, while urging Erdogan’s government “to return to European values”.

The minister said the new steps had been agreed with Chancellor Angela Merkel whose spokesman confirmed that the measures announced by Gabriel against Turkey are necessary and unavoidable in view of developments there.

German Economy Minister Brigitte Zypries echoed similar remarks, saying it is extremely difficult for German companies to make investments in Turkey under the current political climate in the country.

“If respectable German companies are suddenly put on ‘black lists’ and branded as supporters of terrorism then this amounts to a climate that makes new business and investments in Turkey extremely difficult,” Zypries said.