Dutch probe Spanish van found with gas canisters after terror tip

The man "was arrested and taken to the police station," Rotterdam police said in a Tweet, following a tip-off from Spanish authorities.

The arrest came little under a week after twin car-bomb attacks in Spain killed 15 people, in attacks claimed by the Islamic State group.

Dutch bomb squad officials "were investigating the van" which was found just two streets away from the Maassilo concert hall where an American rock band was due to play, they added.

Earlier in the evening Dutch authorities decided to cancel the concert by Californian group Allah-Las in Europe's largest port city after a tip-off from Spanish police around 5.30pm (1530 GMT) about a possible terror attack.

"In the early evening I was warned by telephone that we had received a threat which had implications for an American concert at the Maassilo in Rotterdam," the city's mayor, Ahmed Aboutaleb, told a hastily-called press conference.

"This signal came from the Spanish police to the Dutch police," he added.

But Aboutaleb, the country's first Muslim and immigrant-born mayor who has spoken out against Islamic terror groups, added an investigation was under way and "we cannot say now if the van with the canisters was linked to the threat".

The four-piece band, from Los Angeles, had been escorted from the concert hall by police wearing bullet-proof vests.

In a statement sent to AFP, they said they were "unharmed and are very grateful to the Rotterdam police and other responsible agencies for detecting the potential threat before anyone was hurt."

Rotterdam police said that afterwards an officer "stationed close to the venue decided to stop a van that he saw driving at around 2130 hrs".

"The van had Spanish plates and was driven by a Spanish national. Inside the van were a couple of gas bottles. Whether there is a link with the terror threat is being looked into," the statement in English said, adding "the driver was taken into custody".

The international connections of the cell of mostly Moroccan nationals behind the Spanish attacks are being probed as investigators retrace their movements to France and Belgium.

Spanish police carried out new raids overnight Tuesday to Wednesday after vehicles ploughed into pedestrians on Barcelona's busy Las Ramblas boulevard and a seaside promenade in the resort town of Cambrils.

Fifteen people were killed and more than 120 others were wounded.

Spanish court documents have shown that at least 500 litres of acetone, large quantities of nails and detonators as well as gas canisters were found in raids on a house in the town of Alcanar, south of Barcelona.

The Rotterdam building where Wednesday's concert was to be held, which can hold about 1,000 people, was searched by the Dutch anti-terror squad after the crowd had been evacuated.

The Netherlands has so far been spared from the slew of terror attacks which have rocked its closest European neighbours in past years.

But amid a number of scares here in recent months, and reports that people linked to some of the attacks may have crossed briefly into the country, concerned top Dutch security and intelligence officials have been keeping a wary eye on events.

A spokesman for the Dutch justice ministry told AFP the threat level in The Netherlands remained at "four" out of a possible five.

"Nothing has changed for the moment," Lodewijk Hekking said, meaning the threat levels remains that there is the real possibility of an attack in the Netherlands.