More New Zealand firefighters will be leaving for New South Wales this weekend to lend a hand fighting catastrophic blazes in the state. 

Hundreds of houses have been damaged or destroyed across NSW and Queensland, with local firefighters stretched thin trying to contain the fires.

The fires have so far claimed four lives.

Twenty-six Kiwi firefighters will be departing on Sunday, consisting of six four-person crews, one task force leader and a liaison officer. 

After arriving in Sydney they will be deployed around the state.

The fires have been burning in Queensland and NSW for the past nine weeks. This week has been particularly bad, however, with the greater Sydney area facing "catastrophic" fire conditions.

A state of emergency has been called in NSW, with almost 70 bushfires continuing to burn as of Friday morning.

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"They’re tough firefighting conditions over there at the moment," says Paul Turner, Fire and Emergency New Zealand's national manager of response capability. "The hot, very dry and windy conditions are causing extreme wildfire behaviour."

Despite the difficult conditions, Turner says the Kiwis are happy to lend a hand.

"Fighting fires of this magnitude is a hugely demanding task and we’re happy to continue to support our Australian colleagues when called upon."

The Kiwi crews will be working up to 14-hour shifts in two five-day rotations, with one day of rest between rotations. 

It is also hoped they will gain useful experience.

"Deploying overseas is a valuable development opportunity for those involved and gives them experience in different environments that they can bring back here," says Turner. 

Twenty-five Kiwi firefighters are already in Australia, assisting with air attack, heavy machinery, safety and deployment coordination, Turner said.