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.
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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.
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.