Relations between Turkey and the Netherlands are at their lowest ebb in four centuries because of a row over a Dutch ban on rallies in support of Turkish President Recep Tayyip Erdogan.

A similar refusal by Germany to allow such rallies by Turkish ministers has also angered President Erdogan.

The dispute comes ahead of crucial electoral contests in both Turkey and the Netherlands. The Dutch go to the polls on March 15, with Prime Minister Mark Rutte fighting off a challenge from anti-Islam leader Geert Wilders. The Turkish president plans to hold a referendum in April to increase the powers of his presidency.

What is the dispute about?

It started after both Germany and the Netherlands blocked Turkish ministers from staging rallies in early March to court the votes of expatriate Turks in an April 16 referendum. President Erdogan is seeking support to boost his powers as head of state. A new draft constitution will significantly increase his powers through the creation of an executive presidency and scrapping of the post of prime minister.

The move by Germany and the Netherlands angered President Erdogan, who said the two countries demonstrated Nazi-like behaviour in blocking Turkish officials from campaigning there.

Why are overseas votes important?

The Turkish president has been seeking to harness the diaspora votes, which number as many as 1.4 million in Germany alone. There are an estimated 400,000 Turkish citizens living in the Netherlands.

Although Turkey has 55.3 million people inside the country who are eligible to vote in the referendum and only three million in total living abroad, President Erdogan is not certain of the outcome of the referendum and a defeat could put an end to his power consolidation. So he needs to garner the support of overseas Turkish citizens as well.

He intends to get the votes either through campaigning by his close associates or through fiery rhetoric such as his Nazi accusation - which could resonate with those Turks who feel that Germany is not accepting enough of their religion and ethnicity.

What do others say about the dispute?

The European Union (EU) has urged Turkey to avoid inflammatory rhetoric and warned that its constitutional amendment might harm the country's longstanding bid to eventually join the bloc. Membership talks with Turkey have been moribund, but the prospect of Turkey eventually joining the EU has long been dangled as an enticement to closer ties.

Nato chief Jens Stoltenberg has also urged Turkey and its Nato allies to "show mutual respect, to be calm and have a measured approach to contribute to de-escalate the tensions".

The United States has called on Turkey and the Netherlands to resolve their row. "They're both strong partners and Nato allies. We'd just ask that they not escalate the situation any further and work together to resolve it," said an unnamed senior State Department official.

Timeline of dispute

March 2: The German town of Gaggenau cancels a rally which Turkish Justice Minister Bekir Bozdag is supposed to attend, saying the venue couldn't hold the expected crowd. Frechen, near Cologne, and Cologne-Porz follow suit, cancelling meetings with Turkish Economy Minister Nihat Zeybekci.

The cancellations anger both the ministers and President Erdogan. The Turkish leader labels the German ban as "Nazi practice", threatening to go to Germany personally to campaign.

March 6: German Chancellor Angela Merkel's office rejects President Erdogan's Nazi jibe as "absurd and out of place," but seeks to draw a line under the spat by calling for talks with Turkey.

Another German city Hamburg, citing serious fire safety deficiencies at the venue, cancels an event where Turkish Foreign Minister Mevlut Cavusoglu is scheduled to speak on March 7. The minister insists on going ahead with the visit.

March 7: The Turkish foreign minister, speaking from the balcony of the Hamburg residence of the Turkish consul, tells the German government not to preach about human rights and democracy. After a meeting with German Foreign Minister Sigmar Gabriel, both men agree they want bilateral relations to return to normal. But Mr Gabriel reiterates that "comparisons between the Nazi era and the cancellation of rallies or the rule of law in Germany are unacceptable".

March 8: The Dutch city of Rotterdam cancels a rally due to be attended by the Turkish foreign minister. Mayor Ahmed Aboutaleb says he is informed by the venue's owner that he will no longer make it available for the gathering. Dutch Foreign Minister Bert Koenders also says the Netherlands will "in no way" facilitate the visit by Mr Cavusoglu because of public order concerns.

March 9: A second Turkish minister - Family and Social Affairs Minister Fatma Betul Sayan Kaya - announces plans to visit the Netherlands .

Chancellor Merkel says Germany wants to patch up frayed ties with Turkey, but without compromising its democratic principles or accepting "Nazi" jibes from President Erdogan.

March 11: The Turkish foreign minister insists he will go to the Netherlands to drum up support for the referendum. But the Dutch government refuses permission for his plane to land in the country.

Turkey's family and social affairs minister travels to the Dutch city of Rotterdam by land from Germany. She is stopped just outside the consulate by Dutch police, and after several hours of negotiations, is escorted back to the German border. Pro-Turkey protests break out in Rotterdam.

President Erodogan says The Hague's behaviour is reminiscent of Nazism. The Turkish government summons the Dutch deputy ambassador in Ankara to the foreign ministry in protest. The Dutch embassy in Ankara and consulate in Istanbul are also sealed off for "security reasons", Turkish foreign ministry sources say.

March 12: President Erdogan says he will retaliate in the "harshest ways" against the Netherlands, warning the latter that it will "pay a price". His foreign minister Cavusoglu describes the Netherlands as the "capital of fascism" and says the Turkish government will continue to take steps against the Netherlands until it apologises ove rthe row.

In Rotterdam, Dutch police use water cannons and horses to break up protests over the Netherlands' refusal to allow visits by the two Turkish ministers.

March 13: Turkey summons the Dutch charge d'affaires again. President Erdogan also threatens to impose sanctions on the Netherlands and take it to the European Court of Human Rights over the ban on his ministers speaking at rallies in Dutch cities.

EU foreign policy chief Federica Mogherini and EU Enlargement Commissioner Johannes Hahn call on Turkey to "refrain from excessive statements and actions that risk further exacerbating the situation." But hours later, President Erdogan accuses the German Chancellor of "supporting terrorists" and criticises Berlin for not responding to 4,500 dossiers sent by Ankara on terror suspects. These include those linked to Kurdish militants and the failed coup in Turkey last year.

Later in the day, Deputy Prime Minister Numan Kurtulmus announces that Turkey is suspending high-level relations with the Netherlands and diplomatic flights from the country. It will also not allow the Dutch ambassador to Ankara to return until the Netherlands meets Turkey's conditions over holding rallies.

SOURCES: REUTERS, AGENCE FRANCE-PRESSE, BLOOMBERG, WASHINGTON POST, NEW YORK TIMES