Ankara: President Recep Tayyip Erdogan on Friday urged Turks resident in Europe to have five children, telling the millions-strong diaspora they were the continent's "future" as a bitter dispute festered between Ankara and Brussels.

Turkey and Europe are locked in diplomatic crisis after Germany and the Netherlands blocked Turkish ministers from campaigning for a 'yes' vote in next month's referendum on expanding Erdogan's powers.

Erdogan has repeatedly accused EU states of behaving like Nazi Germany over what he sees as discrimination against Turks, in comments that have caused outrage across the continent.

"From here I say to my citizens, I say to my brothers and sisters in Europe... Educate your children at better schools, make sure your family live in better areas, drive in the best cars, live in the best houses," said Erdogan.

"Have five children, not three. You are Europe's future."

"This is the best answer to the rudeness shown to you, the enmity, the wrongs," he said in a televised speech in Eskisehir, a city south of Istanbul.

Some 2.5 million Turkish citizens resident in Europe are eligible to vote in elections in their homeland. But millions more people living in EU states have Turkish origins.

Erdogan, a father of four, has previously urged women in Turkey to have at least three children to help boost the population, in comments denounced by women's rights activists.

Dutch 'banditry'

Last weekend, just days before the Dutch election, police in Rotterdam used horses and dogs to disperse pro-Erdogan protesters demonstrating against the ban on Turkish ministers.

Erdogan said there was no difference between the tactics used by the police "and the gladiators in ancient Rome."

Several days later, Dutch Prime Minister Mark Rutte saw off a challenge from far-right politician Geert Wilders at the ballot box, to the relief of other EU leaders.

But Erdogan said there was to be no reconciliation with The Hague.

"You use all kinds of banditry for your own ends against a state like Turkey and then you act as if nothing happened and continue as before."

Rotterdam's mayor had initially granted permission for a pro-Turkish protest to take place on Friday over the police's tactics at the weekend, but the organisers later called it off, a city council spokesman said.

Analysts say Erdogan is seeking with his volcanic rhetoric to woo nationalist votes in the April 16 referendum on constitutional change, which analysts believe is heading for a tight outcome.

Also Friday, a Turkish pro-government newspaper ran a front-page mock-up of German Chancellor Angela Merkel in Nazi uniform under the slogan "Frau Hitler".

German deputy government spokesman Georg Streiter refused to be drawn into the controversy, only saying: "We are not taking part in a game of provocation."

'Blow Europe's mind'

Erdogan also lashed out at a decision by the top EU court allowing European firms to ban employees from wearing political or religious symbols -- including the Islamic headscarf.

A day after accusing the EU of starting a "crusade" against Islam by the ruling, he said the court should "ban the kippa ban too" -- although in theory the Jewish skullcap should be included in the decision which covers all religious symbols.

"They are hypocrites!" said Erdogan.

With no end in sight to the tensions between Turkey and the EU which have raised new doubts over Ankara's long-standing membership bid, the government has also threatened to walk away from a key migration deal.

The deal, which was reached on March 18 last year, substantially reduced the flow of migrants to the EU which had peaked in 2015, and was exploited by the European far right.

Interior Minister Suleyman Soylu, a hardliner who is close to Erdogan, threatened to "blow the mind" of Europe by sending over 15,000 refugees a month.

"Let us remind you that you cannot play games in this region and ignore Turkey," he said.

The EU says it expects Turkey to continue implementing the deal.

But the United Nations children's agency UNICEF on Friday said the agreement had been plagued by broken promises, and although it had curbed migrant flows, it had increased the suffering of children.