There's growing concern in Porirua after a group of children were scared by a man dressed as a clown lurking near a school last night.

The three boys were playing basketball at Discovery School in Whitby when they saw the man behind a building.

Police were called to the school about 7.30pm following reports of a man in clown makeup or a mask.

A police spokeswoman said they didn't find anyone matching the description when they arrived and another group of people at the school at the time didn't see anything.

Anyone who sees anything suspicious or threatening is being urged to call police.