Several German nationals are among those being held and Berlin has warned its citizens that their safety cannot be guaranteed in Turkey and that consular access is not assured in case of arrest.
Throwing away any pretence at diplomatic nuance, German Foreign Minister Sigmar Gabriel had Thursday also warned German firms against investment in Turkey and spoke of an "overhaul" of the entire relationship.
"Turkey is a social democratic state based on law and no one has the right to interfere in its internal affairs," said Erdogan before heading off on a trip to the Gulf.
Addressing Gabriel's comments, he said: "We (Turkey and Germany) are together in NATO. We (Turkey) are in negotiations to join the EU.
"So the strategic partnership between us is nothing new. We have been partners for a long time. No step should be taken to overshadow this partnership," he added.
Turkey remains under a state of emergency imposed days after the July 15 failed coup which critics claim is being used to go after any opponent of Erdogan. The authorities say the emergency is needed for public security.
The latest crisis was precipitated by the order of a Turkish court to remand in custody a group of human rights activists detained on an island off Istanbul, including Amnesty International's Turkey director Idil Eser and Berlin-based activist Peter Steudtner.
But Berlin was already furious over the jailing in February of Deniz Yucel, Turkey correspondent for Die Welt newspaper, who Erdogan has personally denounced as a "terror agent".
Meanwhile, Turkey accuses Germany of not doing enough to deal with Kurdish militants and suspects from the failed coup who have taken refuge on its soil.
Erdogan said Ankara had passed Berlin 4,500 dossiers on Kurdistan Workers Party (PKK) suspects alone. Both Turkey and the EU as well as the US outlaw the PKK as a terror group.
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