An attack took place on Monday at an Islamic school in the southeastern city of Eindhoven where a bomb blast caused heavy damage but no injuries.
Five mosques were also targeted by arsonists over the weekend and a sixth was daubed with offensive slogans and pig heads.
Authorities have linked the attacks to the brutal murder on November 2 of Van Gogh by a suspected radical Muslim of Moroccan origin who is in police custody.
Van Gogh was widely-known for his criticism of Islam and recently caused an uproar with a short film linking domestic abuse with the perceived subservient position of women in the Islamic faith.
Five other suspects, all of North African origin, have also been arrested in relation to his murder.
Eindhoven Mayor Alexander Sakkers lamented the escalation in violence on Monday and appealed to calm while Amsterdam's council of churches expressed its solidarity with the Muslim community in an advertisement in the local daily Het Parool.
"Why must such a horrible act [as the killing of Van Gogh] lead to such consequences?" Sakkers was quoted as saying by the Dutch news agency ANP, adding, "We must prevent people from blaming one another."
But a senior Dutch politician, Frits Bolkestein, called on King Mohammed VI of Morocco to condemn Islamist extremism after the murder of Van Gogh. "The king of Morocco must come out against Islamist extremism," said Bolkestein and show clearly that his country "does not want to be an exporter of murderers."
Muslim houses of worship and Islamic schools have been under surveillance since Van Gogh's murder but police patrols would be stepped up, Sakkers said.
Eindhoven has some 20,000 Muslims inhabitants in a total population of 210,000 people.
Driss Al Boujoufi, deputy head of Ummon association, which oversees some 90 Moroccan mosques in the country, also said that security had been boosted at places of worship and schools.
Meanwhile an internet site set up for condolences following Van Gogh's murder was forced to shut down because of a flood of racist messages. But several far-right marches in Amsterdam failed to attract a large crowd.
Out of a population of 16 million the Netherlands has some 900,000 Muslims and of those some 300,000 are of Moroccan descent.
An Islamist group has threatened to make the Netherlands "pay dear" for reprisals against Muslims, according to an Islamist website. "We will not just stand by in the face of what is happening at our schools and mosques in Holland," a self-styled Al Tawhid Al Islami group wrote. "We want official apologies to the Muslim community, if not you will pay dear."
© 2004 Agence France-Presse
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