Rescue services and troops in New Zealand are working around the clock to help those affected by a severe storm that has sparked flooding and led to the evacuation of hundreds of homes.

Key points: States of emergency in Christchurch, Otago, Timaru and Dunedin

States of emergency in Christchurch, Otago, Timaru and Dunedin Troops called in to help emergency services

Troops called in to help emergency services Several rescued from floodwaters

A state of emergency has been declared in the South Island cities of Christchurch, Otago, Timaru and Dunedin after some areas were hit with more than 200 millimetres of rain in 24 hours.

In Christchurch, the Heathcote River burst its banks and flooded southern parts of the South Island city on Saturday morning,

By late on Saturday night waters were receding slightly and rain was expected to reduce significantly.

However, people still in their homes in flooded parts along the river have been told to stay indoors.

The New Zealand Defence Force deployed at least a dozen trucks and 140 personnel to provide emergency services and help rescue those trapped by floodwaters.

Homes in the Henley township in the Otago region were inundated with water. ( Facebook: Otago Regional Council )

Fire and rescue officer Mark Bradford said while flooding was the main issue in Christchurch, some houses were affected by landslides.

"We've had actually had quite a few slips, landslides coming down against houses," he said.

"There's been about three of them so far over the last 12 hours, some houses have been evacuated from there."

He said crews had rescued several people stranded in floodwaters.

Rain had been expected to gradually ease throughout the day. ( ABC News: Phil Rogers )

Those evacuated near Christchurch were told not to return home until at least Sunday.

New Zealand Prime Minister Bill English said his "thoughts are with those affected by the weather events".

"Please follow official advice and take care of each other," the Prime Minister tweeted.

Otago Regional Council says the floodway at Otokia has been performing as planned. ( Facebook: Otago Regional Council )

A front is forecast to move up the South Island on Monday, then to weaken as it crosses the North Island overnight Monday, the New Zealand MetService said.

The weather front is forecast to move to the east of the country by Tuesday.

In good news for the rugby-mad nation, however, a Super Rugby quarter-final between Dunedin and Christchurch on Saturday night went ahead.

The Crusaders made the most of the tough weather conditions, playing a dominant game to hold the Hurricanes scoreless in their 17-point victory.

Dozens of roads in Christchurch are closed due to flooding. ( Facebook: Christchurch City Council )

The flooded State Highway 1 south of Christchurch. ( Facebook: NZ Transport Agency - South Island )

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Reuters