German Chancellor Angela Merkel has said that she would ask the European Union to call off membership talks with Turkey, amid escalating tensions between Berlin and Ankara. Merkel's tough stance came after Turkey arrested two more German citizens last week for political reasons, infuriating Berlin. <br/><br/>The arrests brought the number of German political prisoners in Turkish custody to 12, at a time when ties between the two NATO allies were already at an all-time low. The plunge in relations began after Berlin sharply criticised Ankara over the crackdown that followed last year's failed coup attempt. <br/>'<br/>Turkish President Recep Tayyip Erdogan, for his part, has also sparked outrage after charging that Germany is sheltering plotters of last year's coup, as well as Kurdish militants and terrorists, and demanded their extradition. <br/><br/>Erdogan added to the tensions this month when he urged ethnic Turks in Germany to vote against Merkel's conservatives and their coalition partners, the Social Democrats, in September elections. <br/>