THE HAGUE (AFP) - A Dutch anti-racism activist is facing trial for hurling abuse at the monarchy during a protest, an official said Wednesday.

Abulkasim al-Jaberi was arrested on November 16 last year in Amsterdam during a protest at the start of the traditional gift-giving festival of Saint Nicholas.

The festival features a character named Zwarte Piet in Dutch, or "Black Pete".

Activists say the character, usually in blackface, is a racist display of a stereotype dating from the colonial era.

Defenders of the tradition say Black Pete is black from coming down the chimney.

Television footage showed Jaberi using foul language in slogans referring to King Willem-Alexander and the rest of the royal family. He was then detained by police.

"He has to appear before an Amsterdam judge... for deliberately insulting the king according to Dutch law," said Loes Gerrits of the prosecutor's office.

"He did receive a 500 euro (S$751) fine, but he declined to pay. Therefore, he must now face court," on May 27, she said.

It is a crime to deliberately insult the Dutch king or a member of the royal family, punishable with a fine of up to 20,000 euros or a five-year prison sentence.

But offenders are seldom prosecuted in the Netherlands, which puts a high premium on free speech.

Jaberi's lawyer Willem Jebbink said his client was "completely bewildered" by the charge.

"My client is against Black Pete and held a speech during the demonstration. In his speech he made a comparison between Black Pete and our slave history... and attributed it to the royal house," said Jebbink.

Evert Boerstra, another prosector's office spokesman, said a decision had been taken to prosecute Jaberi, as his words "had nothing to do with the anti-Black Pete demonstration".