WELLINGTON, Feb 15 (AFP) - Cyclone Gabrielle weakened and moved away from New Zealand on Wednesday (Feb 15) as the country started to assess the damage caused by significant flooding, landslides and high winds that left three people dead and displaced thousands from their homes.

Gabrielle, which reached New Zealand on Sunday before making its way down the east coast of the North Island, cut off entire towns, washed away farms, bridges and livestock, and inundated homes, stranding people on roof tops.

"We thankfully are through the worst of the storm but we're not out of danger yet," Emergency Management Minister Kieran McAnulty said during a televised media briefing.

"This is a significant disaster and is going to take many weeks for those areas most affected to recover ... we are in this for the long haul."

Residents in hard-hit areas are now being asked to conserve water and food because of fears of shortages after the cyclone forced New Zealand on Tuesday to declare a national state of emergency for only the third time in its history.

Parts of New Zealand's North Island, where about 75 per cent of the country's 5 million residents live, are enduring their second major storm in as many weeks. Record rains last month triggered flash floods and four people lost lives then.

Emergency crews on Wednesday found the body believed to be that of a volunteer firefighter who had been missing since Sunday night following a landslide at a beach community near the country's largest city of Auckland, authorities said.

Two other people have been confirmed dead in Hawke's Bay, a region on the eastern coast of the North Island. Authorities estimate more than 10,000 people have been displaced so far.

Helicopters winched people stuck on rooftops to safety, while military planes will be used to deliver essential supplies to isolated towns, McAnulty said.