Finance Minister Wolfgang Schaeuble was quoted on Friday as comparing Turkey with the former communist East German state and saying Berlin might have to tell Germans travelling there that they did so at their own peril.

Foreign Minister Sigmar Gabriel told Germans on Thursday to exercise caution if travelling to Turkey and threatened steps that could hinder German investment after the NATO ally detained rights activists.

The arrests were part of a broader crackdown across Turkish society since a failed coup last July.

"If Turkey does not stop playing this little game, we need to tell people: 'You travel to Turkey at your own risk - we can't guarantee you anything anymore,'" Schaeuble told the mass-circulation Bild newspaper.

Schaeuble compared Turkey to the former German Democratic Republic (GDR), East Germany: "Turkey now makes arbitrary arrests and no longer sticks to minimum consular standards. That reminds me of how it was in the GDR."