Rescue services and troops in New Zealand are struggling to cope with the aftermath of a massive storm that prompted hundreds of evacuations, triggered mudslides and inundated the South Island with floods that have seen hundreds of homes evacuated.

A state of emergency declared on Saturday for the cities of Christchurch, Otago, Timaru and Dunedin remains in effect, although authorities were cautiously optimistic by the wee hours of Sunday, saying that flooding had peaked and the worst appeared to be over.

In just 24 hours some areas were hit with more than 200 millimetres of rain, causing the Heathcote River to break its banks and swamp a low-lying swathe of Christchurch’s suburbs.

Emergency workers reported that flooding hit its peak late Saturday and had receded slightly by the wee hours of Sunday, with further relief anticipated if rainfall peters out, as forecasts predict.

Fire and rescue officer Mark Bradford said while flooding was emergency workers’ primary concern, landslides around Christchurch were also a concern as sodden hillsides slipped and gave way under the weight of their soaked topsoil.

“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.”

The New Zealand Defence Force poured troops and equipment into the flood zone to assist civilian teams rescuing those isolated by floodwaters.

“Please follow official advice and take care of each other,” the Prime Minister Bill English tweeted.

-with wires and ABC