Some children who have spent time in Syria are considered to be so dangerous they are to be included on the official security service watch list, the Volkskrant says on Wednesday.

Rob Bertholee, the head of Dutch intelligence, told a conference in Berlin this weekend that the Dutch authorities have identified 70 minors who have travelled to Syria and Iraq.

Officials have now confirmed that youngsters can be added to the terrorist watch lists, the Volkskrant says. The children will be included in a separate register which can also be shared with foreign governments.

The AIVD said in its document Leven bij ISIS (living with Isis) published earlier this year that children aged as young as nine have been recruited for combat training.

Bertholee did not say if any of the child fighters have returned to Europe, NBC said. The decision to include minors on terror watch lists is because ‘we cannot rule out any scenarios’.

Most of the Dutch children have been taken to the Middle East by their parents although around one-third were born there. More may have been born in Syria and Iraq but the AIVD says it is difficult to assess how many.