The number of people still unaccounted for in the wake of Cyclone Gabrielle that battered New Zealand nearly two weeks ago has dropped to 13, authorities said on Saturday, as heavy rain overnight prompted evacuations on the country's North Island.

Gabrielle struck the island's northernmost region on February 12 and tracked down the east coast causing widespread havoc, leaving at least 11 dead and displacing thousands.

The number of people who couldn’t be contacted exceeded 6,000 following the cyclone as communications were knocked out in many areas but that has receded amid recovery efforts.

"Getting in touch with those remaining 13 remains a priority for police and we are working as fast as we can," New Zealand police said in a statement early on Saturday.

In Hawke's Bay, one of the areas worst hit by Gabrielle, heavy rains overnight brought a renewed flood risk to the region where an evacuation order was in place, Hawke's Bay Emergency Management Group said.

Homes in the Esk Valley had "been unoccupied since the cyclone, but an additional 26 households evacuated yesterday", the agency said.

About 680 kilometers north, at the town of Mangawhai in Northland, more than 200 people sheltered in camps on Friday night as rain caused landslides that blocked road exits, Radio New Zealand reported.

The wild weather also triggered flash floods and evacuation warnings in and around Auckland, the nation's largest city with a population of around 1.6 million.

New Zealand weather forecaster MetService said some of the heaviest rain was recorded in Auckland, with 155mm (6.1 inches) recorded there in the past 24 hours.

The forecaster had a heavy rain warning in place on Saturday for large swaths of the North Island's east coast, including Hawke's Bay.

"Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and [landslides] are also possible and driving conditions may be hazardous," it said.

It said it was also "closely monitoring" a tropical low near Fiji that could turn into a tropical cyclone next week.