"Nazi comparisons offend our honour!" he said, referring to previous exchanges between Ankara and Berlin, in which Turkish President Recep Tayyip Erdogan repeatedly accused the German government of employing "Nazi practices".
Foreign ministry spokesman Martin Schaefer told reporters it had "specific indications" that the two Germans, a married couple, had been taken into police custody over the weekend.
Other strains include local German authorities' refusal earlier this year to allow rallies by Turkish politicians ahead of a referendum on the Turkish president's powers.
"The nightmare continues that is facing so many German citizens who wanted to do nothing but spend their vacation in Turkey", said Schaefer.
German Chancellor Angela Merkel called anti-immigration demonstrators "rowdies" driven by intolerance, her strongest reaction yet to protests that have disrupted many of her election rallies this summer.
"Then Turkey would join a list of countries such as Libya, Yemen and Syria in which no one would think of going on holiday".
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This will be the fourth edition of the Big Billion Day, and will be held from September 20 to 24, just ahead of Dussehra.
Relations further deteriorated after the detention of several German citizens including Deniz Yucel, a correspondent for Die Welt newspaper. Here, we have freedom of expression and the rule of law.
Schaefer said those travelling to Turkey should be aware of the potential dangers, but said Berlin had no immediate plans to issue a formal travel warning.
Germany had updated foreign ministry travel advice in July to warn citizens that they could face arrest if they travel to Turkey.
According to the statement of the Turkish foreign ministry the German political leaders' pre-election campaign is based on anti-Turkish principles.
Both Merkel and her chief rival in the September 24 national election, Martin Schulz, had called for an end to Turkey's European Union membership negotiations during a TV debate last week.