New Zealand Defence Force (NZDF) headquarters is closed due to earthquake damage, with officials refusing to say when staff might return.

The building, on Aitken St near Parliament, typically has around 1200 people working in it, mostly from the NZDF, as well as several hundred Ministry of Defence employees.

RNZ reported on Wednesday that staff who work in the building have been told it has been declared uninhabitable and that they may not return for a year. One source said staff would not be back in the buildings before Christmas.

Wing Commander Neil Taylor would only say that the building was closed. He gave no indication of when or whether it would reopen.

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"The building is closed at the moment. We're going through the normal engineering review processes," Taylor said.

NZN Defence Force headquarters in Wellington has been deemed uninhabitable following Monday's earthquake.

"We'll have some more information in the next day or so as to where things will go."

Taylor declined to say what the initial engineering assessment suggested.

"I can't be specific...as to what is going to happen."

FAIRFAX NZ Defence House on Aitken St is closed, with reports staff have been told they will not be back in the building for a year.

Other NZDF sites were operating as normal and some staff have been relocated to ensure critical functions were continued.

"People are either working from home; we've got a few people at the likes of Trentham, moved up there, just to keep the essential bits running," Taylor said.