ANKARA: Relations between Turkey and Germany, which have been tense since last year, worsened further lately as the two NATO allies and key economic partners are locked in acrimony over a ban preventing Turkish ministers from addressing expats inside Germany to campaign for constitutional reforms granting extended powers to President Recep Tayyip Erdogan. Turkish voters will go to the polls on April 16 to approve or reject constitutional amendments to transform the nation’s parliamentary system into a presidential one. Germany, home to over 3 million out of 5 million people of Turkish origin in Europe, is a key factor in the political campaign. With some 1.4 million voters, it is a must-go spot for members of the Turkish government. Erdogan, who had campaigned in Germany in 2011 and 2014, was reportedly planning a another political rally to secure the important diaspora before the referendum. The German government under Chancellor Angela Merkel is under increased pressure from the opposition and the press to reject such Turkish campaigns inside the country, especially after a reporter of the prominent newspaper Die Welt, Deniz Yucel, became the first German citizen to be arrested last month for what was described as “terrorist propaganda” as part of Erdogan’s crackdown in the wake of the failed coup last summer. The journalist has been accused personally by Erdogan of being a “German agent” and a member of the Kurdistan Workers’ Party (PKK).