UPDATED 4.14pm A Whangarei man is fighting for his life in Auckland Hospital after being being struck on the head with a piece of wood yesterday.

Detective Senior Sergeant Dene Begbie said the serious assault happened at a house in William Jones Dr, Otangarei yesterday afternoon shortly after 3pm.

The 42-year-old victim was left with critical injuries after he was struck on the head with a piece of wood.

He was taken through to Whangarei Hospital but transferred to Auckland Hospital where he underwent surgery last night.

Begbie said he was in a critical condition and had life-threatening injuries.

Police had spoken to a number of witnesses and were following positive lines of enquiry.

A scene examination of the Whangarei property was underway.

Police had erected a cordon around a vehicle and a blue tent covered the vehicle at the side of the Otangarei house.

Police appealed for anyone at the address or any members of our community who were in the area and witnessed any suspicious activity to contact Whangarei Police Station on 09 430 4500 or anonymously on 0800 555 111.