Staff have been evacuated from the Prime Minister's Auckland electoral office after a sword was used to damage the building this morning.

Police said the incident took place at about 8.20am when an object was thrown through a window at the office in Morningside, police said.

A sword was later photographed lying outside the office on New North Rd.

"No injuries have been reported and the building was unoccupied at the time," police said.

"A scene examination will be conducted and inquiries remain ongoing."

Damage done to the Prime Minister's office. Photo / Dean Purcell

The door that was damaged at the Prime Minister's office. Photo / Dean Purcell

The sword was seen by passers-by lying on the ground.

The Prime Minister is currently in Antarctica.