Vandals have damaged art works on display on Waiheke Island.

The works are part of the Headland Sculpture exhibition, a free public event that opened this weekend.

The targets have included the winning work, The Precariats, by Cushla Donaldson - and at least two other pieces.

The Precariats is a large work that invites people to play it like a percussion instrument.

The artist describes the attack as "sad".

Security and volunteer guide numbers have now been boosted.