Several people were shot in the Dutch city of Dordrecht "in a very serious" incident early on Monday evening, Dutch officials said.
No details were immediately available and it was unclear if there were fatalities.
Dordrecht Mayor Wouter Kolff said on Twitter there had been "a very serious shooting incident" and that he was heading to the scene.
Police could not confirm local media reports of three fatal victims in the city, near the port of Rotterdam.
Police said emergency response teams were at the scene to treat victims and investigate the shooting.
