Emergency services are at Prime Minister Jacinda Ardern's electorate office in the Auckland suburb of Morningside which appears to have been vandalised overnight.
A person at a neighbouring business said police officers were on the scene when he arrived at work this morning.
He said the office in New North Road had been cordoned off.
A spokesperson for the prime minister said her office was aware of the incident but waiting on further details.
Ardern is currently in Antarctica.
A police spokesperson said the incident was reported about 8.20am when an object was thrown through a window at the office.
No injuries had been reported and the building was unoccupied at the time.