A decapitated doll was left at a mosque in Amsterdam, police said, in an Islamophobic act that has shocked the Muslim community in the Netherlands.

The head was hung by a rope from a fence above the doll's "bloodstained body", pictures showed, and a note was left warning against "Islamisation" in the Netherlands.

An employee of Emir Sultan Mosque found the doll as he opened the place of worship on Thursday morning, and reported it to the police.

The note on the doll, apparently referencing Turkish President Recep Tayyip Erdogan, said: "Islam is inextricably linked with brutal beheadings. Islamisation must stop. No to the Diyanet mega-mosque in Amsterdam-Noord (north), which is connected to dictator Erdogan."

The Emir Sultan Mosque serves a predominately Turkish community in the north of Amsterdam.

In a statement to Dutch media, the Emir Sultan Islamic Foundation called it a "cowardly and disgusting act".

"Of course we are shocked and condemn this cowardly attack, but we do not let ourselves be intimidated and played against each other," the statement said.

"We will continue to profile ourselves as part of society and continue to work for the preservation of peace and solidarity in Amsterdam-Noord. We request everyone to keep their cool and wait for the police investigation," it added.

Kamber Sener, president of the mosque, wrote on Facebook, asking the community "not to worry about this incident".

"I hope they will find the perpetrators as soon as they can," he wrote, asking for the city to unite against such acts.

The act was claimed via Twitter by a right-wing group calling itself Rechts in Verzet, or Right in Opposition.

The group tweeted photos of the doll and the note to several Dutch news organisations, adding in the tweet: "Beheading! No mega mosque in Amsterdam-Noord. Protest."

The person running the Twitter account was also under investigation, Amsterdam's local TV channel AT5 reported.

The protest group had previously criticised the arrival of a mega-mosque in Amsterdam-Noord.