Turkey's presidential spokesman Ibrahim Kalin slammed German authorities on Saturday for allowing PKK supporters to rally in the city of Frankfurt.
About 9,000 people were at the event organised by the German Democratic Kurdish Society Centre (NAV-DEM).
The demonstration was in opposition to Turkish President Recep Tayyip Erdogan and an April referendum on increasing presidential powers.
Protesters chanted "Terrorist Erdogan" and "freedom for Ocalan," referring to Abdullah Ocalan, the imprisoned leader of the PKK, with many waving flags featuring Ocalan's face.
Turkey, the EU and the US consider the PKK a terrorist group and it is banned in Germany.
Kalin said Germany was treating terrorists as "legitimate actors," while claiming it was "dangerous" for Turkey's elected representatives to meet with their constituents.
"It is clearly supporting terrorism," Kalin added. "Those who try to explain this hostile attitude with freedom of expression and assembly should act seriously."
The presidential aide accused some European countries of attempting to "interfere [in] the referendum that will take place on April 16 in Turkey and taking up a position in favour of a 'No' vote."
"We once again remind European countries that Europe will not decide on April 16, the Turkish nation will."
Critics condemned Germany on Twitter for allowing the PKK supporters to rally.
Democracy in Germany has room for those who speak for terror organization PKK, but not for those who speak on behalf of Turkish government. pic.twitter.com/0A4DKRZUX3
— YusufYerkel (@YusufYerkel) March 18, 2017
1. Unbelievable! After banning Turkish ministers from 'yes' campaigning, Germany allows terrorist pkk to hold a mass 'no' rally in Frankfurt pic.twitter.com/Ng4z8WiXfP
— Gulnur Aybet (@Gulnuray) March 18, 2017
Today in Germany. Police protect rally of Marxist PKK terror supporters. Last week Germany banned Turkish politicians from speaking: pic.twitter.com/T62KZU3XX9
— Ed Husain (@Ed_Husain) March 18, 2017
The Turkish president and governing AK Party are seeking support for the referendum among Turkish citizens abroad.
President Erdogan strongly criticised Germany after Turkish ministers were barred from holding public rallies in two German cities in recent weeks, calling the ban a throwback to the era of fascism in Europe and Nazism in Germany.
Erdogan also slammed German authorities for letting opposition to a 'yes' vote in the referendum hold rallies while preventing his emissaries from addressing expatriate Turkish communities.
On Wednesday, German foreign ministry spokesman Martin Schaefer said the government had approved voting by the estimated 1.4 million Turkish nationals living in Germany who are eligible to cast ballots in the April 16 referendum.