The European Union on Monday, March 13 warned President Recep Tayyip Erdogan to avoid inflammatory rhetoric as a diplomatic crisis between Turkey and the Netherlands deepened over the blocking of Turkish ministers from holding rallies to win support for plans to expand his powers, AFP reports.

Erdogan at the weekend twice accused NATO ally Netherlands of acting like the Nazis, comments that sparked outrage in a country bombed and occupied by German forces in World War II.

Dutch Prime Minister Mark Rutte, who faces a major challenge from the far-right in a key general election Wednesday, said Erdogan's comments were unacceptable and it was Ankara that should apologise.

In an escalating standoff that risks damaging Turkey's already deteriorating relations with the European Union ahead of the April 16 referendum on constitutional change, Brussels sternly warned Ankara to avoid making the situation worse.

In apparent reference to Erdogan's comments, EU foreign policy chief Federica Mogherini and EU Enlargement Commissioner Johannes Hahn called on Turkey to "refrain from excessive statements and actions that risk further exacerbating the situation.

"It is essential to avoid further escalation and find ways to calm down the situation," their statement added.

NATO chief Jens Stoltenberg 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".