THE HAGUE—Dutch police arrested seven people Thursday on suspicion of planning a "terrorist" attack in Amsterdam after a threat that caused shop closures and the cancellation of a rock concert.

The seven — six men and a woman between the ages of 19 and 64 — "are suspected of preparing for the commission of crimes with a terrorist objective," Amsterdam police spokeswoman Charmain van Damme told AFP.

All of the suspects have dual Dutch and Moroccan citizenship, and one was related to a suspect in the 2004 Madrid train bombings that killed 191 people and wounded more than 1,800, said another spokeswoman, Hanane Lechkar.

Earlier, police commissioner Bernard Welten told a news conference in the capital that police received a telephone call on Wednesday night "warning that three men were planning to carry out an attack with explosives in Amsterdam."

The caller gave the names and addresses of the men in question and the stores they intended to attack. The homes of the seven suspects have been searched.

The call came from Brussels and named home furnishing retailers Ikea among other large stores to be targeted.

Following up on the information, police on Thursday morning prevented dozens of shops, a movie theatre and the Ikea store from opening their doors to the public "to prevent any explosives from entering," said Welten.

Amsterdam mayor Job Cohen told journalists that Wednesday's call had warned of "an action with the aim of claiming casualties in busy places.

"We couldn't take any risks," he said about the closure of shops, adding that "we do not yet have sufficient information to lift" the security measures.

The officials would not say anything about the caller's motives or the veracity of the threat.

A police statement earlier said the threat, which it said "should be taken seriously" had caused an appearance by American band The Killers at the Heineken Music Hall to be postponed.

Dozens of shops remained closed throughout the day. Most had not yet opened their doors in the morning when the area was closed off. Several employees were evacuated.

Wim Kok, a spokesman for the office of the national anti-terrorism coordinator, told AFP there was no reason to raise the terror alert.

Janna Langlere, a promoter for the Arena Boulevard affected by the closure, said the threat was received by Ikea in the morning, apparently aimed at all "megastores."

"This is a lost business day. We have had telephone calls about claims for damages (by shop owners), and it is being looked into."

According to police reports, the shops will be open again as usual on Friday, as there is no further threat to public safety.

AFP/Radio Netherlands/Expatica