Voting in Turkey's referendum to consolidate power in the presidency began in Germany on Monday, allowing roughly half of the 3 million residents to cast their ballots until April 9.

Turkish citizens residing in Germany are able to cast their votes in several cities across the country, including Berlin, Munich and Cologne. In Turkey, eligible voters will be able to cast their ballots on April 16.

Read more: Turkish constitutional reform: 5 important points

The referendum has soured relations between Berlin and Ankara after authorities canceled several rallies where Turkish officials were expected to speak in favor of the constitutional amendments.

Turkish President Recep Tayyip Erdogan responded by accusing the German government as well as Chancellor Angela Merkel of engaging in "Nazi practices."

He has accused European authorities of launching a "crusade" against Islam and said the continent was hosting the "spirit of fascism."

"Europe is swiftly rolling back to the days before World War II," he said in a speech aimed at rallying support for the proposed constitutional amendments.

'Destroyed years of integration'

Several German officials, including Merkel, have lashed out at Erdogan's comments, saying they effectively undermine relations between the two nations.

German Finance Minister Wolfgang Schäuble on Sunday told the Berlin-based "Die Welt" newspaper that Erdogan's repeated remarks targeting Germany have marked a "bitter setback."

"In a short period, he has deliberately destroyed years of integration in Germany. Repairing the damage being made will take years," Schäuble said, referring to generations of Turkish-origin Germans.

EU-Turkish spat simmers on A battle between the cross and the half moon? President Recep Tayyip Erdogan has repeatedly accused Dutch and German politicians of acting like "Nazis" and claiming the "spirit of fascism" is rampant in Europe. He later invoked medieval religious wars in the context of escalating tensions between the EU and Turkey. "My dear brothers, a battle has started between the cross and the half moon. There can be no other explanation," Erdogan said.

EU-Turkish spat simmers on Never let a crisis got to waste Turkish Foreign Minister Mevlut Cavusoglu, meanwhile, was not to be outdown by his boss. Speaking on Thursday, Cavusoglu said Europe was losing its unity. "Religious wars will soon begin in Europe... If things continue as they are, then it will be so." "You will learn how to behave towards us. If you do not learn, we will teach you."

EU-Turkish spat simmers on Indefatigable, as ever German Chancellor Angela Merkel welcomed the election victory for the center-right prime minister Mark Rutte in divisive Dutch elections. "I was very happy that a high turnout led to a very pro-European result, a clear signal," she said. "I don't intend to participate in this race to trade provocations." Referring to Erdogan's attacks, she added: "The insults need to stop."

EU-Turkish spat simmers on Ratchet down, not up Meanwhile, Germany's Interior Minister Thomas de Maiziere said Ankara was playing the victim with its attacks on its NATO allies to galvanize support ahead of its referendum in April. Turkish politicians had "no business" campaigning in Germany, he said. France and Germany plan to establish a European center to counter extremist propaganda and deradicalize young people, he also revealed this week.

EU-Turkish spat simmers on Rutte stems the populist tide After a week of heightened tensions between Turkey and the Netherlands, Dutch Prime Minister Mark Rutte emerged victorious in a bruising battle with Geert Wilders. The populist's invective against all things Muslim and anything from the EU failed to earn him the breakthrough that many had come to count on as a given.

EU-Turkish spat simmers on Hollande happy over Holland French President Francois Hollande congratulated Rutte for his election success and his "victory against extremism." He said that "the values of openness, respect for others, and a faith in Europe's future are the only true response to the nationalist impulses and isolationism that are shaking the world." In a joint statement with Angela Merkel, he denounced Erdogan's remarks as "unacceptable."

EU-Turkish spat simmers on Paris: next stop on the populist express After boosts in Britain and the United States over the past year and Wednesday's setback in the Netherlands, populism now heads to France for its next test of political viability. Now it is for Marine Le Pen of the National Front to carry the torch in presidential elections starting next month.

EU-Turkish spat simmers on Right message, wrong ring tone? Meanwhile, Germany's far-right kept on message. "I can not hide the fact that we wanted Wilders to have had a better result," the leader of the populist Alternative for Germany (AfD) Frauke Petry said. "Wilders addressed the right issues in the election campaign, but he might not always have had the right tone. Citizens want a clear message, but they are afraid of a hard tone," Petry said.

EU-Turkish spat simmers on Moscow fans the flames Konstantin Kosachev, chair of the Foreign Affairs Committee in the Russian parliament, wrote that Europe had been "weakened" by the elections in the Netherlands. "French Presidential candidate Emmanuel Macron and Merkel may breathe for the time being after the victory of Rutte, but the fear among the established European elites facing the challenges of the 21st century remains palpable," he wrote.



Consolidating power?

In January, Turkey's parliament passed the 18-article bill, paving the way for the referendum, which seeks to transition the country into an executive-style presidential system.

The reforms would effectively abolish the post of the prime minister and allow the president to belong to a political party, which is currently forbidden.

Human rights groups have criticized the proposed amendments to the constitution, saying they further erode the rule of law in the wake of a failed coup last year.

"The proposed constitutional changes concentrate power in the hands of President Erdogan and further erode already weak checks and balances on the exercise of that power," said Hugh Williamson, Europe and Central Asia director at Human Rights Watch, in January.