The US government has advised its citizens to ‘exercise increased caution’ when travelling to the Netherlands following the stabbing of two American tourists by a suspected terrorist during the summer.

The State department raised its travel advisory alert from level 1 to level 2 in response to the incident at Amsterdam Central Station on August 31. The two 38-year-old victims were attacked by a 19-year-old Afghan national living in Germany.

The advice said terrorists were continuing to plot possible attacks in the Netherlands. ‘Terrorists may attack with little or no warning, targeting tourist locations, transportation hubs, markets/shopping malls, local government facilities, hotels, clubs, restaurants, places of worship, parks, major sporting and cultural events, educational institutions, airports, and other public areas,’ it said.

Domestic agencies, including the police and Amsterdam city council, have not brought in security measures in the wake of the stabbing incident. The attacker, named only as Jawed S., is thought to have chosen his victims at random as they queued at a service counter.

Mohammed cartoons

Police said they were able to react quickly after specially trained ‘spotters’ in the station observed S.’s ‘unusual behaviour’ in the minutes before the attack. Earlier in the day he posted a video online in which he accused Dutch politician Geert Wilders of insulting Islam while a Dutch flag burned in the background.

Wilders had called off a contest the day before to draw cartoons of the prophet Mohammed, which had been the subject of violent street protests in Pakistan.

S’s lawyer, Simon van der Woude, said his client had expected to die in the attack. A will was found at his home in Germany. German media said youth care services had noticed changes in S.’s behaviour earlier this year that suggested he had radicalised, such as growing a long beard.