Turkey summoned Germany's ambassador to express its fury over a Frankfurt rally where protesters brandished insignia of outlawed Kurdish militants, the presidential spokesman said Sunday, denouncing it as a "scandal".
Some 30,000 pro-Kurdish protesters attended Saturday's rally where demonstrators called for a 'no' vote in an April 16 referendum on expanding President Recep Tayyip Erdogan's powers.
Many carried symbols of the outlawed Kurdistan Workers Party (PKK) which has been fighting a bitter insurgency against the Turkish state for over three decades.
"Yesterday (Saturday), Germany put its name under another scandal," presidential spokesman Ibrahim Kalin told CNN-Turk, complaining about the open use of insignia of the "separatist terror group" -- the PKK.
"Yesterday, the German ambassador was invited -- was summoned -- to the foreign ministry and this was condemned in the strongest way."
He said the demonstrators had used the upcoming Kurdish New Year festival of Newroz as a "pretext" for the rally as the new year only falls on Tuesday.
The foreign ministry had on Saturday accused the German authorities of blatant hypocrisy for allowing the protest despite preventing Turkish ministers from campaigning there for a 'yes' vote.
Turkish officials noted that the protesters had waved banners of a group that is itself illegal in Germany, with the ministry saying that allowing the rally to go ahead was the "worst example of double standards".
Many protesters carried portraits of the PKK's jailed leader Abdullah Ocalan, who is serving a life sentence in Turkey, calling for his release.
Tens of thousands of people have been killed since the PKK launched its insurgency against the Turkish state in 1984, initially seeking independence for Kurds in the southeast and then for greater autonomy and rights.
The group is listed as a terror organisation not just by Turkey but also the European Union and the United States.
The ban on Turkish officials campaigning in various European states has triggered a crisis in Ankara's relations with the EU.
Erdogan has accused Germany and the Netherlands of behaviour reminiscent of Nazi Germany while Berlin has in turn expressed revulsion at his comments.