Pro-Palestinian protesters have splashed red paint on the outside of the US Consulate and Ministry of Foreign Affairs buildings in Auckland.
A group calling itself Tamaki for Palestine said the paint symbolised blood on US and New Zealand officials' hands following the death of thousands of people in Gaza.
It claims the current tensions did not start on 7 October with the Hamas attack in Israel.
It is calling on the US Ambassador in New Zealand to be expelled and New Zealand's envoy in Washington to be brought home.
As well as the red paint, the words 'Ceasefire Now' were tagged on the buildings.
Police say they are making enquiries into vandalism at two addresses, one on Customs Street and one on Quay Street.
They were called to a report of vandalism at the Quay Street building about 1.50am.
One person has been arrested.
In Wellington, graffiti has appeared on the fence of Premier House this morning.
The house, in the central suburb of Thorndon, is the official residence of the prime minister.
'Stop the genocide', 'free Gaza' and 'Stop supporting ISRAEL' are tagged in red spray paint.
'We also stand with Palestinian civilians' - US Embassy
The US supported the right of people to voice their opinion through peaceful protest but civil protests "do not include vandalizing property", a United States Embassy spokesperson said.
"As we stand with the people and government of Israel, we also stand with Palestinian civilians."
They said the US recognised "the legitimate aspirations of the Palestinian people, and we support equal measures of justice and freedom for Israelis and Palestinians alike", reiterating US President Joe Biden's comments.
"We know the humanitarian situation is urgent, and we continue to focus on addressing the humanitarian needs of civilians in dire need.
Quoting US Secretary Antony Blinken, the spokesperson said: "Addressing the humanitarian crisis in Gaza ... aligns with our nation's most deeply held principles, including our belief that every civilian life is equally valuable and equally worthy of protection - no matter what his or her nationality, ethnicity, age, gender or faith. A civilian is a civilian is a civilian."
MFAT declined to comment.