ANKARA/ISTANBUL (Reuters) - Turkish President Tayyip Erdogan on Tuesday warned the Netherlands that he could take further steps in a deepening diplomatic row, while a government spokesman in Ankara said economic sanctions could be coming.

Incensed by Dutch and German government bans on his ministers from speaking to rallies of overseas Turks, Erdogan also accused German Chancellor Angela Merkel of siding with the Netherlands in the fight between the NATO allies.

Turkey suspended high-level diplomatic relations with the Netherlands on Monday, banning the Dutch ambassador from the country and preventing diplomatic flights from landing in Turkey or using its airspace.

Those steps were taken after Erdogan branded the Netherlands “Nazi remnants” at the weekend for muzzling his ministers.

“The cabinet took action yesterday but there are many other things that could be done against the Netherlands,” Erdogan said in a speech broadcast live on television.

“We will show those who think they can get away with an apology that they are making a mistake,” said Erdogan, who is campaigning for an April 16 referendum on boosting his powers and has been looking to the large number of Turks living in Europe to help secure victory.

Deputy Prime Minister Numan Kurtulmus later told broadcaster CNN Turk that economic sanctions could be in the works.

“Pressure will continue against the Netherlands until they make up for what they did. We’ve started with the political, diplomatic sanctions, and economic sanctions may follow,” he said.

Erdogan has threatened to take the Netherlands to the European Court of Human Rights over the ban on his ministers, which both the Dutch and Germans have imposed citing fears of unrest.

Dutch police used dogs and water cannon on Sunday to disperse hundreds of protesters waving Turkish flags outside the consulate in Rotterdam. Some protesters threw bottles and stones and several demonstrators were beaten by police with batons, a Reuters witness said. Mounted police officers charged the crowd.

SAARLAND, BELGIAN BANS

The small western German state of Saarland said on Tuesday it would ban political campaigning by foreign politicians.

“Internal Turkish conflicts have no place in Germany. Election appearances which put at risk domestic peace in our country must be banned,” State Premier Annegret Kramp-Karrenbauer said in a statement.

A street vendor sells flags during a protest in front of the Dutch Consulate in Istanbul, Turkey, March 12, 2017. REUTERS/Murad Sezer

“The atmosphere that has been created by Nazi comparisons and insults must not be allowed to escalate,” she said.

The Belgian city of Antwerp said it would not allow a politician from the nationalist MHP party to speak at an event, although Ali Guler was still set to appear on Sunday at a Turkish restaurant in Genk, in the east of the country.

While Turkish law forbids election campaigning abroad and in diplomatic missions, ministers are circumventing the ban by holding what they say are cultural events with Turkish citizens.

Erdogan has said that those who oppose the referendum, are aligning themselves with terrorists. He has also accused European states, including Germany, of harbouring terrorism, an allegation they deny.

SHARP WORDS FOR MERKEL

EU states are also unhappy with what they see as an increasingly authoritarian tone from Turkey and the spat is likely to further dim Ankara’s prospects of EU membership.

EU foreign policy chief Federica Mogherini and EU enlargement commissioner Johannes Hahn called on Turkey to moderate its language and avoid further escalating the dispute.

Erdogan renewed his attack on Merkel after she criticised his “Nazi remnants” jibe against the Dutch.

“The countries that have embraced this thuggery have lost all their credibility. The Chancellor of Germany has come out and said she supported the Netherlands. We know that you are no different than them,” Erdogan said.

Dutch Prime Minister Mark Rutte said the Turkish sanctions, while “not too bad”, were inappropriate as the Dutch had more to be angry about.

Ankara’s foreign ministry said the European Union was exercising democratic values selectively.

“It is very grave for the EU to hide behind member country solidarity and stand by the Netherlands, which has clearly violated human rights and European values,” it said.