People pose for photographs on a rooftop in Istanbul. The Turkish president has criticized Berlin for blocking several rallies in advance of an April 16 constitutional referendum | Chris McGrath/Getty Images Erdoğan attacks Merkel again Relations between Ankara and Berlin continue to worsen.

Turkish President Recep Tayyip Erdoğan on Sunday re-upped his attacks against German Chancellor Angela Merkel, accusing her of using “Nazi measures” as the dispute between Berlin and Ankara intensified, according to media reports.

"You are right now employing Nazi measures," Erdoğan said in a televised speech on Sunday, using the informal 'you' in Turkish, according to Agence France-Presse. "Against who? My Turkish brother citizens in Germany and brother ministers," he said.

The Turkish president has previously criticized Berlin for blocking several rallies in advance of an April 16 constitutional referendum that would greatly expand his powers. "Your practices are not different from the Nazi practices of the past," he said.

Turkish ministers may plan another rally in Germany ahead of the vote on Erdoğan's powers, the presidential spokesperson İbrahim Kalın said on Sunday, a move that could further ignite tensions. Kalın made the comment in an interview with broadcaster CNN Türk, Reuters reported.

On Sunday, the Turkish president also accused a jailed Turkish-German journalist of being a terrorist agent, adding: "Thank God he has been arrested," he said, according to Reuters. Erdoğan, who was speaking at a meeting of an Islamic foundation in Istanbul, said the reporter, Die Welt newspaper's Deniz Yücel, would be tried in Turkey.

Separately, in a move sure to further anger Turkish officials, Bruno Kahl, the German foreign intelligence chief, said in an interview on Saturday that Turkey "failed to convince" Germany that Fethullah Gülen's organization was behind last year's coup attempt. Ankara has accused Gülen, a religious leader who lives in self-imposed exile in the U.S. of orchestrating the July 15 coup attempt in which about 300 people died. "Turkey has tried to convince us of that at every level but so far it has not succeeded," Kahl was quoted as saying by German news magazine Der Spiegel.