A 12-year-old boy has been killed and an 11-year-old seriously injured in an accident involving explosives in Haaksbergen, a small town in Overijssel.

Police say the boys were innocent bystanders and that one person has been arrested in connection with the incident.

A police spokesman said the children had been watching someone using a home-made hammer system to ignite explosives during a street party involving four families in the Albert Cuypstraat.

A klaphamer is a self-made way of igniting explosives using a metal hammer construction with a small tray for the power, often magnesium. Klaphamers are a popular tradition in the Twente region and are legal in the Netherlands.

Police are still investigating exactly what went wrong. According to the Telegraaf, the boys may have been passing by when the explosives went off.

Another popular Dutch tradition at New Year is carbidschieten – the practice of mixing carbide and water in a milk churn with a lid so it explodes.