German authorities withdrew permission last week for two rallies by Turkish residents in German cities amid growing public outrage over Ankara's arrest of a Turkish-German journalist, dragging bilateral ties to a new low.
The planned rallies were part of a Turkish government campaign to win support among Germany's 1.5 million-strong Turkish community for sweeping new presidential powers going to referendum in April 16. The German authorities cited security concerns.
"Germany, you have no relation whatsoever to democracy and you should know that your current actions are no different to those of the Nazi period," Erdogan said at a rally in Istanbul. "When we say that, they get disturbed. Why are you disturbed?"
Relations between the two NATO partners have deteriorated sharply since a failed July coup bid against Erdogan, when Ankara accused Berlin and other capitals of failing to condemn rogue military elements quickly or convincingly enough.
Erdogan, accused by critics of increasingly authoritarian tendencies, has accused Germany of harboring enemies of Turkey, from Kurdish militants to coup organizers.
He has been sharply criticized in western Europe for mass dismissals and arrests of suspected conspirators, from judges to journalists.
Germany has demanded the release of a German journalist arrested in Turkey whom Erdogan described as a "German agent".
Local media reported that Turkish Economy Minister Nihat Zeybekci planned to attend two events in Germany on Sunday, in Leverkusen and Cologne in the state of North a, which has a large Turkish population.
Germany is Turkey's most important trading partner in the European Union, which Ankara officially aspires to join.