Updated: 6.45am, 24/08
The driver of a van - registered in Spain - is being held by Dutch police after gas cylinders were found inside the vehicle near a concert venue in Rotterdam.
A US rock band called the Allah Las were due to perform at the Rotown venue in the city.
The venue said the concert was cancelled by order of the police, and the building was cleared.
Update: het gaat om een terreurdreiging, de Maassilo wordt momenteel ontruimd. Kaarthouders zullen uiteraard hun geld terug krijgen.
— Rotown (@rotownrotterdam) August 23, 2017
Police confirmed the concert was called off in connection with "a terror threat."
They said the decision was made to cancel the event after consultation with the venue, and an investigation has been launched.
The city's mayor, Ahmed Aboutaleb, said a small van with Spanish licence plates and "gas bottles" was found near the venue.
He added that it was not clear whether the terror threat and the van were connected.
Rotterdam Police confirmed a Spanish van driver was detained, and taken to a police station.
The incident comes as Spanish police continue their investigation into the twin terror attacks which took place on August 17th.
Fifteen people were killed and 120 others were wounded in the attacks which took place on Barcelona's Las Ramblas district and in the coastal town of Cambrils.
Additional reporting: IRN