The Hague (AFP) - Rotterdam police have arrested a Dutchman found with a loaded AK-47 Kalashnikov rifle and illegal fireworks who is "suspected of preparing a terrorist crime," prosecutors said Friday.
The 30-year-old was detained on Wednesday after police raided his apartment following a tip-off from the Dutch intelligence services, also seizing a painting with a picture of the flag used by the Islamic State group, mobile phones and some 1,600 euros ($1,700) in cash.
It comes with European cities on their guard following deadly attacks in Paris and Brussels and amid warnings that a current all-out offensive against IS in Iraq could see dozens of hardened fighters return home.
Rotterdam police found the gun, two loaded magazines and four boxes of illegal fireworks during the raid, prosecution spokesman Wim de Bruin told AFP.
"He's suspected of preparing such a terrorism crime, but we don't have information about the specific details," De Bruin told AFP.
The man has been taken into custody for questioning and Friday appeared before Rotterdam magistrates. He will appear in court again in two weeks.
Rotterdam is Europe's busiest port, and one of The Netherlands' most multi-cultural cities, home to many who have emigrated from abroad.
Dutch law enforcement agencies have been on high alert since the November 2015 bombings in Paris, and the March suicide attacks on the Brussels metro and airport. Both France and Belgium neighbour the small northern European country.
- Returning fighters -
Last week, the European police agency Europol warned that terror networks such as IS are evolving their tactics to attack soft targets across the continent.
And the European Union said this week that around a third of the estimated 5,000 European jihadists who went to Iraq and Syria have returned to Europe.
The EU report said there were two types of "foreign terrorist fighters" returning.
"Those in the majority that will drift back, and those who will be sent back on specific missions, which are of most concern," the report warned.
About 270 Dutch people left to join the jihadists, and about 40 former fighters are known to have returned from combat in Syria and Iraq, where most have been fighting against Syrian President Bashar al-Assad's regime.
Another 190 Dutch citizens including women and children are still in Syria and Iraq, the Dutch counter-terrorism agency said in a report last month while 44 fighters have been killed.
"The number of returning jihadist fighters will pick up should the 'caliphate' be militarily defeated or collapse," the agency said in its latest "Terrorism Threat Assessment".
"An increased number of returnees will most likely strengthen the jihadist movement within The Netherlands and therefore increase the threat posed by this group," it said.
Two recent scares saw a partial evacuation of the busy Schiphol airport, near Amsterdam, just three weeks after the Brussels bombing, when a drunken man falsely said he had a bomb in his backpack.
And last month, police swooped on Rotterdam airport in a clampdown which also turned out to be just a scare.