Radical Islamist groups in the Netherlands have become a decentralized and elusive "swarm" that may broaden their focus from the conflict in Syria to the wider Middle East, the Dutch intelligence service warned on Monday.
Its report reflects widespread concern in Europe at the threat posed by European citizens - mainly from Islamic immigrant milieus - leaving to fight in Middle East conflicts, then returning battle-hardened and posing security threats.
Dutch authorities estimate that 120 Dutch citizens have fought in Syria's civil war, with 14 having died in combat, and that there are hundreds of jihadi militants in the country eyeing missions abroad, with thousands more sympathizers.
The Dutch General Intelligence and Security Agency (AIVD) said in its latest assessment of the threat posed by underground jihadi groups that they were stronger and more self-confident.
It said such militants continued to pose a "substantial" threat to the Netherlands, one notch below the highest alert.
Most of the potential fighters were of Moroccan background although some were native Dutch converts to Islam.
The agency said the phenomenon was becoming ever harder to track as social media made it possible for increasingly "professionalised" radical movements to coordinate themselves without the need for a centralised authority.
"The movement has taken on the character of a swarm," the agency said. "There is a less hierarchical structure than at the turn of the millennium, which makes it more flexible, effective and less vulnerable to 'attack' from outside."
European governments have struggled to stop their nationals, some just teenagers, from traveling to Syria where the conflict, which began as peaceful protests against President Bashar al-Assad and evolved into an armed rebellion is now in its fourth year. More than 160,000 people have been killed.
CRACKDOWN ON WOULD-BE JIHADIS
An 18-year-old man was recently arrested in The Hague on suspicion of recruiting people to take part in the Syrian conflict, the Dutch anti-terrorism coordinator said on Monday. Dutch authorities have blocked student grants and welfare payments to more than 30 people suspected of preparing to join wars abroad, and frozen the assets of several others. Other measures under review include stripping suspected militants of their Dutch nationality. A draft law has been submitted for review to the country's highest legal advisory body, Justice Minister Ivo Opstelten told parliament on Monday. "It is unacceptable for Dutch citizens to take part in the jihadist movement and in violent jihad, regardless of where it takes place," he said in a letter. "All possible means will be used to disrupt travel plans, to reduce the risk posed by those returning and to prevent recruiting of new supporters."
Prosperous and with an economy that recovered and grew fast after World War Two, the Netherlands opened its doors to immigration from Morocco and Turkey in the 1960s, and today some 5 percent of the population is of Islamic heritage.
But as growth has slowed and jobs become scarcer in recent years, radical Islam has gained currency in some immigrant communities, raising the concern of state authorities.
The Dutch intelligence service warned that radicals in the Netherlands might turn their attention towards fighting in other current or potential Middle East conflict zones.
"For now, Dutch jihadis are heavily focused on Syria, but that could change," the AIVD report said. "It could involve existing conflict zones likes Yemen and Iraq, but even potential new zones like Egypt - including Sinai, or Libya."
Would-be fighters in Middle East conflicts are growing more skilled at evading the attention of authorities, buying return tickets to the region and posing as tourists, it said.
"News from conflict zones in Syria is spread rapidly via chat, Facebook and email within hours or even in real time within a jihadi inner circle in the Netherlands," said the report. It added that the number of jihadist publications in Dutch had increased sharply over the past two years.
The French citizen suspected of shooting dead four people at the Jewish Museum in Brussels in May spent time fighting in Syria. The Dutch report said some 3,000 European had gone to Syria to fight alongside Islamist rebels.
The Brussels attack "illustrates that the threat posed by returning jihadist fighters is Europe-wide," Opstelten wrote. "That means that there is a risk posed by all returning Syria fighters, also to the Netherlands."