By Jane Wardell
WELLINGTON (Reuters) - The tail-end of powerful Cyclone Debbie, which left a trail of destruction in northeast Australia, lashed New Zealand on Tuesday, closing highways and causing a major landslip.
The storm hit parts of New Zealand still recovering from a devastating earthquake last November and weather officials warned of several days of heavy rain, with some regions set to receive three months' worth of rain in the next 48 hours.
"This is a significant amount of rain and people are advised to watch out for rapidly rising rivers and streams, flooding and slips," the Met Office said in a severe weather warning.
As darkness fell, a state of emergency was declared in the city of Whanganui on the North Island, with its mayor warning that mandatory evacuations were likely at first light as rivers were forecast to rise to dangerous levels.
"We have about 20 hours to save your precious things, maybe raise things, maybe check on your elderly neighbour," the mayor, Hamish McDouall, said in a statement.
Weather officials issued a swathe of rain and wind warnings covering the entire North Island and top of the South.
Cyclone Debbie, a category four storm, one short of the most powerful level five, pounded Australia's Queensland state last week, smashing tourist resorts, bringing down power lines and shutting down coal mines.
Australian police on Tuesday retrieved three bodies from a car beneath floodwaters in the swollen Tweed River of New South Wales state, taking to six the number of people killed since the storm hit.
New Zealand's mountainous terrain makes its roads susceptible to landslides and many regions are still recovering from November's 7.8-magnitude quake.
The highway into the quake epicenter of Kaikoura was closed on Tuesday, just hours after reopening following a week-long closure to shore up almost 20 potential slip sites. A second major arterial road was blocked by a landslip.
New Zealand's Civil Defence Force was on standby as other roads were closed and at least one school was evacuated.
In Australia, where the disaster zone stretched 1,000 km (600 miles) from Queensland's tropical resort islands and Gold Coast tourist strip to the farmlands of New South Wales, about 20,000 homes were still without power on Tuesday, as flood waters continued to rise in some areas.
Residents of Rockhampton, in central Queensland, were advised to seek higher ground as the rising Fitzroy River approaches a peak forecast for Thursday. Australian insurers have declared the event a catastrophe, with state officials saying recovery and repairs will need months.
(Additional reporting by Tom Westbrook in SYDNEY. Editing by Sandra Maler and Michael Perry)