The Turkish military invaded northern Syria in January to attack a Kurdish militia group it has labelled a "terrorist group."
Thousands of Kurdish demonstrators marched through the German city of Hannover on Saturday against Turkey's military offensive in Syria.
The demonstrators were also protesting against German arms sales to Turkey.
Many chanted "Terrorist Erdogan get out of Kurdistan," referring to the Turkish president who ordered the offensive last month against a Kurdish militia group based in northern Syria.
That group, the YGP, have been fighting so-called Islamic state in Syria alongside the US military.
Some demonstrators waved flags showing the leader of the banned Kurdistan Workers' Party, known as the PKK, and police say they are evaluating videos to see if they can determine their identity.
The PKK has been fighting for three decades for greater autonomy for Turkish Kurds in Turkey.