Some 300 Dutch nationals have had their passports cancelled since autumn 2014, the Dutch counter terrorism chief Dick Schoof told Radio 1 on Wednesday.

Most of those involved had already gone to Syria or Iraq. Now their passports have been cancelled, the authorities will be alerted if they attempt to cross back into the Netherlands or use their travel documents elsewhere.

In addition, the passports of several dozen people who are suspected of planning to travel to IS-held territory have been cancelled. Schoof said he hopes this will prevent them from leaving the country.

So far, some 40 people have come back to the Netherlands after spending time in Iraq and Syria, Schoof said. ‘We are extremely alert to this,’ he said. ‘We don’t know why they have come back. It could be that some regret what they have done, but we won’t take any risks.’