At the beginning of the month, Erdogan called out Germany and the Netherlands for using Nazi tactics to keep their population under control, especially the Turkish immigrants.
Merkel retorted on the 9th of March, saying that he had to stop spreading such lies.
Now, over the weekend, he accused Merkel personally of using Nazi techniques to keep Turkish immigrants under control and "all Europeans want to open up gas chambers, but don't have the courage." He also accused her, and the German parliament of supporting terrorists (while they refuse to condemn the PPK and not stop them speaking out in public).
On the other side, the German Government have said that the Turkish sponsoring of religion through government is not allowed in Germany (the church and politics are strictly separated by law), but Erdogan's government pours millions every year into Mosques in Germany.
The Turks have a very large minority in Germany, around 5 million German citizens or residents, who are also eligible to vote in Turkish elections. This means that it is a very big group for the Erdogan to try and win over. Given his efforts at home to silence the press (the arrest of Deniz Yücel, for example), he and his party are not welcome guests in Germany and he is furious, that Germany, and Europe in general, doesn't also ban all negative comments about him and his party. Last week some campaign speeches in German were cancelled.
http://www.heute.at/news/welt/Erdogan-b ... 61,1409781