Police have arrested the man they suspect killed filmmaker Theo van Gogh, as well as some 15 alleged members of the group, including six apprehended last week in an apartment siege in The Hague. More arrests are expected.
Edwin Bakker is a terrorism expert at the Clingendael institute, a foreign policy research center based in The Hague.
"They were looking for a group called the 'Hofstad Group.' This is a group of persons to which the person who allegedly killed Van Gogh was part of. And these are partly youngsters. Some of them were born and raised in the Netherlands. Two of them have American fathers. Others are foreigners, illegals. So it's a mixed group of young people," Bakker said.
Van Gogh, well known for his critical views of extremist Islam, was a distant relative of the famed painter Vincent Van Gogh. He was shot and stabbed to death while bicycling in central Amsterdam on 2 November -- a date that many Dutch now refer to as their "11 September."
The murder has rocked race relations in historically tolerant Holland, sparking tit-for-tat arson attacks against mosques and churches.
The suspected killer, a Dutch-born Moroccan known as "Mohammed B," was detained shortly after the murder. He was later revealed to have contacts with local terrorist cells.
The Hofstad group is believed to have ties with militants in Spain and Switzerland. Analyst Bakker says a Syrian member of the group is still at large.
"But there is one -- [or rather] a few central figures: a Syrian person who was believed to be their somehow sheikh a scholar, who informed them and taught them about Islam and of course certain fundamentalist views on Islam. And there is also evidence that persons who were involved in terrorist attacks in perhaps Spain, [or] perhaps Casablanca, Morocco, were also part of that group or had contacts with them," Bakker said.
Media reports say that European countries were on the trail of militants linked to the slaying for months before it happened, but lacked evidence to break up the cell until it was too late.
Professor Cees Wiebes is a lecturer at the University of Amsterdam and has good contacts to the Dutch security services. He says it appears the Hofstad group was also planning to kill leading politicians.
"There were various groups, various persons who had the idea of killing two important members of parliament [who] have very clear, outspoken opinions about what should be done with radical Islam and radical Islamic persons in the Netherlands. [The politicians] had been voicing this criticism [against] certain mosques, which they consider as too radical for some years now. On Islamic websites [these politicians] had been targets for quite some years now. But [concerning] these persons who are arrested, the police more or less revealed that they were trying to [kill] these politicians," Wiebes said.
One of those politicians is Geert Wilders, a right-winger who favors closing down offensive mosques and deporting clerics who hold views at odds with Dutch law. The other is Ayaan Hirsi Ali, of Somali descent. Hirsi Ali -- now under police protection -- co-wrote a film with Van Gogh strongly criticizing Islam's treatment of women.
Some unconfirmed reports also say militants may have been planning to kill Amsterdam's Jewish mayor, Job Cohen, and deputy mayor, a Moroccan man who favors integrating Muslim immigrants into Dutch society.
But Wiebes cautions against jumping to conclusions about the involvement of international terrorism, especially concerning Van Gogh's alleged killer. Wiebes says Mohammed B. was an amateur -- not a highly trained professional.
"[Mohammed B was] kind of an amateur. I mean, a couple of weeks before he committed this act, he was arrested in a streetcar in Amsterdam for refusing to pay for his ticket. Well, [that's very] stupid if you are a potential terrorist. Then you should have a very low cover. He started to make havoc in the streetcar and then the police arrested him. They found a notebook, they found addresses, they found telephone numbers, emails. It was not very good from the standpoint of operational security," Wiebes said.
The concern now is that rising fears over terrorism could aggravate existing tensions between the majority Dutch population and the nearly million-strong Islamic minority.
A recent poll showed that 40 percent of the Dutch now "hope" that Muslims "no longer feel at home" in the Netherlands.
Van Gogh's murder sparked a series of reprisals against Islamic targets, including the firebombing of mosques. Churches in turn have also been attacked, and rising ethnic tensions have also been seen in neighboring Belgium, where an orthodox Jew was shot dead yesterday.
Another high-profile killing in Holland could see the situation deteriorate further.