The 18-year-old Amsterdam youth picked up in December for planning to carry out a school shooting told judges on Thursday that the threats which led to his arrest were ‘a joke’.

Mitchell O’s trial was suspended for a time on Thursday because the youngster was not in court. Although this is not compulsory in the Dutch justice system, the judge ordered that he be brought to the court room in the interests of the case.

During the hearing, to decide if O should be remanded in custody for a further three months, the court was told Dutch police were alerted to him by the FBI. He had also been spoken to by police about his online behaviour.

‘I understood what they were saying but that is the sort of joke I make,’ local broadcaster AT5 quoted O as saying. ‘Other people know that, and I thought they would forget all about it.’

O was arrested after placing a English-language video on YouTube saying he was making preparations to shoot at a school. On his phone were films of school shootings, bomb attacks and other incidents.

A spokesman for the public prosecution department stressed that the teenager had not said any particular school was a target.