Turkish President Recep Tayyip Erdogan on Friday told Germany it cannot scare Ankara with threats, in an escalating row over a wave of arrests that prompted Berlin to step up warnings to German tourists and investors.

"They (Germany) cannot scare us with these threats, they should know this," Erdogan said in a speech in Istanbul, also responding to criticism saying Turkish courts were "more independent" than German ones.

"Germany should sort itself out," he added.