Police are investigating overnight explosions at two Polish supermarkets in Heeswijk and Aalsmeer.

The explosion in Aalsmeer happened at around 3am, and caused a fire which also spread to the upstairs flat and a car. No-one was injured, broadcaster RTL reported.

The second explosion took place in Heeswijk-Dinther, south of Den Bosch, an hour later. That blast hit the front wall of the store and damaged nearby shops as well. Twenty people living in apartments above the shops were evacuated but have since been allowed home after experts said the property was safe.

Police explosives experts are at the scene on Tuesday morning looking for trace evidence and to try to determine what triggered the blasts.

The supermarkets were initially reported to be part of the Polish discount chain Biedronka but a spokesman for the company has told DutchNews.nl that this is not the case and that the group does not operate outside Poland.

Mohamad Mahmoed, owner of the Aalsmeer supermarket along with his brother, told broadcaster NOS that he had no idea who would want to damage his business and that he had no connection with the other supermarket which was attacked.

Aalsmeer mayor Gido Oude Kotte said the attack had shaken up the neighbourhood. ‘We have been faced with a sort of terrorist act this morning,’ he told the broadcaster.