Germany has threatened Turkish politicians with a ban on public appearances, in an escalating diplomatic spat between Ankara and Europe.
The diplomatic crisis was sparked when the Netherlands and Germany refused to allow Turkish ministers to address rallies to court the votes of Turkish citizens living in their countries for an April 16 referendum to enhance President Recep Tayyip Erdogan's powers.
Erdogan responded by accusing Germany of "Nazi practices" and blaming the Dutch for the 1995 Srebrenica massacre in Bosnia.
Foreign Minister Sigmar Gabriel told Der Spiegel magazine that Berlin will take "necessary measures if Ankara does not abide by German law."
"Those who cross the line cannot assume that they can propagate their political views here," he said in remarks published on March 18.
Turkish Foreign Minister Mevlut Cavusoglu said European leaders were barring Turkish politicians from campaigning in their countries because they feared a stronger Turkey.
"They are enemies of Turkey and they look after the traitors, the terrorist organizations," Cavusoglu was quoted as saying by the state-run Anadolu news agency.
Erdogan has accused Berlin of supporting Kurdish terrorist groups in Turkey, an allegation German Chancellor Angela Merkel called "absurd."
Merkel warned Turkish leaders on March 16 that "the insults must stop."
Erdogan, speaking at a World War I memorial event in western Turkey on March 18, said he would "continue to stand tall" in the face of actions by Europe.
On March 16, Turkish Interior Minister Suleyman Soylu threatened to send 15,000 refugees to the European Union and warned it could cancel a March 2016 deal with the EU to curb the influx of refugees to the bloc.
A German government spokesman said on March 17 that there were no signs that the deal had been suspended by Ankara.
With reporting by dpa and Der Spiegel