Kurdish supporters in Frankfurt protest against Erdogan

People hold placards during a demonstration organised by Kurds, in Frankfurt, Germany, March 18, 2017. REUTERS/Ralph Orlowski

FRANKFURT (Reuters) - Around 30,000 Kurdish supporters demonstrated in the German city of Frankfurt on Saturday against Turkish President Tayyip Erdogan and an April referendum that would give him sweeping new powers.

Protesters chanted "Erdogan terrorist" and "freedom for Ocalan", referring to Abdullah Ocalan, the jailed leader of the militant Kurdistan Workers Party (PKK), with many waving flags featuring Ocalan's face.

The European Union and United States consider the PKK a terrorist group and it is banned in Germany.

"The Europeans should hear us, empathize with our suffering and help us. It would be best if they imposed economic sanctions on Turkey," demonstrator Sinan Anin said.

The protest brought swift condemnation from Turkey, which said Germany was allowing open support for terrorism.

"We strongly condemn the German authorities for allowing the demonstrations by PKK terrorist supporters," Ibrahim Kalin, Erdogan's spokesman, said in a statement.

He said Germany was treating terrorists as legitimate actors while calling meetings between Turkish politicians and citizens in Germany "dangerous", a reference to the recent ban in German cities on referendum rallies by Turkish politicians.

Police in Frankfurt, where hundreds of officers were deployed to the event, described the protest as peaceful and said on Twitter that most of the demonstrators had complied with German laws, adding: "We want to guarantee they can exercise their fundamental rights."

On Wednesday Martin Schaefer, spokesman for the Foreign Ministry, said the German government had approved voting by the estimated 1.4 million Turks living in Germany who are eligible to cast ballots in the April 16 referendum.

Erdogan is seeking support among Turks abroad for the referendum. German Foreign Minister Sigmar Gabriel has said Erdogan is taking advantage of a sentiment many people of Turkish origin have in Germany that they are neither accepted nor welcomed.

Demonstrator Mustafa Bostan said if Erdogan won the referendum, things would worsen: "It could be that he'll say: 'I've won again' and then he'll start fighting again and destroying Kurdish towns or killing Kurds."

Relations between Ankara and Berlin have been burdened by the arrest of a Turkish-German journalist in Turkey and by Erdogan's description of the bans on planned rallies by Turkish ministers as "fascist".

(Reporting by Reuters Television; Additional reporting by Tulay Karadeniz in Ankara; Writing by Michelle Martin; Editing by Dale Hudson and Julia Glover)