Dutch police have arrested four men including a Swedish citizen suspected of being involved in terror-related activities, prosecutors said on Tuesday.
"Rotterdam police detained four men early on Sunday evening on suspicion of being involved in terrorism," the public prosecution's office said in a statement.
One of the men, aged 29, arrived on a flight from Stockholm earlier Sunday while the other three aged 21, 23 and 30 come from the cities of Vlaardingen, Delft and Gouda in southwest Netherlands.
Dutch police raided three homes in the three cities and seized data but found no weapons or explosives, the statement said.
Although "there is no concrete information to indicate a terror attack, police and the public prosecution's office are not taking any chances," prosecutors said without giving further information.
The suspects remain in custody pending a court appearance.
A Dutch citizen was sentenced to four years in November for preparing a terror attack following his arrest in Rotterdam last year, when police discovered an assault rifle and a large amount of fireworks.
In another scare, Dutch military police shot and wounded a man armed with a knife at Amsterdam's Schiphol airport earlier this month, but authorities said the incident was not terror-related.
The Netherlands has so far been spared from the slew of terror attacks to have rocked its closest European neighbours in recent years.