Ancient Moriori tree carvings have been vandalised at a historic reserve on the Chatham Islands.
The carvings, or rakau momori, are between 200 and 500 years old and have been slashed, possibly with a machete.
The general manager of the Hokotehi Moriori Trust, Maui Solomon, was one of a group who discovered the vandalism during a conservation exercise on Thursday morning.
Mr Solomon says the eyes and head of the human figure were specifically damaged - an action particularly hurtful to Moriori.
The chair of trust, Shirley King, says its important that someone is held accountable and, though she has some idea who may have carried out the vandalism, proof is needed.
A substantial reward has been offered for information leading to a successful prosecution.
Mrs King says the damage represents a loss to Moriori, the nation and the world, as there are no other memorials like the tree carvings.
Prominent archaeology lecturer Ian Barber from the University of Otago says the carvings are an expression of the Moriori belief system and a record of important ancestors.
He says the vandalism is an attack on the nation's culture.