Turkey summoned Germany's ambassador to express its anger over a Frankfurt rally where protesters brandished insignia of the outlawed Kurdistan Workers' Party (PKK), the presidential spokesman said March 19, France24 reported. Some 30,000 pro-Kurdish protesters attended the March 18 rally where demonstrators called for a 'no' vote in an April 16 referendum on expanding President Recep Tayyip Erdogan's powers. Turkey has been locked in a feud with Germany and the Netherlands after both countries prevented its ministers from addressing rallies of expatriate Turks, citing safety concerns. The ban on Turkish officials campaigning has triggered a crisis in Ankara's relations with the European Union. There is also a possibility that Turkish ministers could plan another rally in Germany ahead of the referendum, Erdogan's spokesman said, Reuters reported. The move could further heighten tension with Berlin.