Some 30,000 Turkish Kurds have held a demonstration in the German city of Frankfurt against the Turkish President, Recep Tayyip Erdogan.
Protesters came from all over Germany ahead of Kurdish new year celebrations.
They called for democracy and a No vote in next month's Turkish referendum on increasing presidential powers. Many carried symbols of the banned PKK.
Turkey condemned the gathering as "unacceptable" and accused Germany of hypocrisy for allowing it.
A diplomatic row has been escalating between the countries since Germany refused to let Turkish ministers hold pro-government rallies in the country two weeks ago.
Mr Erdogan's spokesman Ibrahim Kalin said in a statement: "It is unacceptable to see PKK symbols and slogans... when Turkish ministers and lawmakers are being prevented from meeting their own citizens.
"We once again remind European countries: on April 16 the decision is to be made by the (Turkish nation), not Europe."
A police spokesman described Saturday's rally in Frankfurt as peaceful.
Many of the demonstrators carried banners of the outlawed Kurdistan Workers Party (PKK), which has battled the Turkish state for more than three decades.
More than 40,000 people have been killed since the PKK launched its insurgency in 1984, and the European Union and United States both consider it a terror organisation.
About 1.4 million Turks in Germany can vote in the April referendum, which could give Mr Erdogan new powers over the budget and the appointment of ministers and judges, as well as the power to dismiss parliament.
Waning EU hopes
On Monday Mr Erdogan stepped up a week of anti-German rhetoric by accusing Chancellor Angela Merkel of "supporting terrorists".
Her spokesman described the jibe as "clearly absurd".
He also accused Germany of "Nazi practices" for blocking his ministers from speaking in Germany.
Senior German officials have cast doubt on Turkey's chances of joining the EU, as it continues to claim it is being treated unfairly by countries in western Europe.
In an interview published by Hamburg weekly Der Spiegel, Germany's foreign minister suggested that the most Turkey can hope for is to one day achieve a "privileged partnership" with the EU.
"Turkey is further away than ever before from EU membership," Sigmar Gabriel was quoted as saying.
The verdict came after Mr Erdogan urged Turks living in Europe to deploy a baby boom as a response to Europe's "injustices".
Speaking in the city of Eskisehir, he addressed "his brothers and sisters in Europe", saying: "Have not just three but five children. The place in which you are living and working is now your homeland and new motherland. Stake a claim to it.
"Open more businesses, enrol your children in better schools, make your family live in better neighbourhoods, drive the best cars, live in the most beautiful houses."
The comments have angered German nationalists, who responded by calling for an end to dual citizenship.