Germany and Turkey have been caught up in a fresh spat after a rally backing outlawed Kurdish fighters in Turkey was held in Frankfurt and a top German intelligence official made controversial comments on last summer's failed coup against the Turkish government.
There is a possibility that Turkish ministers could plan another rally in Germany ahead of an April 16 referendum on changing the constitution, President Tayyip Erdogan's spokesman said on Sunday, a move that could further heighten tension with Berlin.
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.
"We strongly condemn the German authorities for allowing the demonstrations by PKK terrorist supporters", Ibrahim Kalin, Erdogan's spokesman, said in a statement.
"The German ambassador was invited - was summoned - to the Foreign Ministry and this was condemned in the strongest way", he said.
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.
Kahl also said he did not think the Turkish government was behind the coup, saying: "The coup attempt was not initiated by the government".
About 300 people, vast majority of them civilians, were killed after rebel soldiers attempted to overthrow the government on July 15, bombing state buildings and killing civilians and security forces.
In an interview with Der Spiegel published on Saturday, Germany's foreign intelligence chief Bruno Kahl said Ankara had repeatedly tried to convince Berlin that Gulen was behind the coup "but they have not succeeded".
The European Union and United States consider the PKK a terrorist group and it is banned in Germany. More than 240 people died in the attempt.
Erdogan is seeking support among Turks overseas for the referendum.
Turkey is accusing Germany of supporting the network of a USA -based Muslim cleric it blames for last year's attempted coup - comments likely to aggravate a diplomatic feud between the two countries.
Iyimaya said that certain European countries act in an obvious way against the constitutional changes that will be put into referendum next month.