Cyclone Gabrielle swept away roads, inundated homes, and left 225,000 people without power in New Zealand, as a national state of emergency was declared on Tuesday.

Strong winds and driving rain lashed the country’s populous North Island, in what Prime Minister Chris Hipkins called the “most significant weather event New Zealand has seen in this century”.

“The impact is significant and it is widespread,” he said. “The severity and the damage that we are seeing has not been experienced in a generation.”

The severity was revealed in daylight on Tuesday, with roads eaten away by landslips and collapsed homes buried in mud, silt and a slew of storm detritus. Falling trees smashed power lines and floodwaters blocked several major roads, leaving communities stranded.

Local media reported some people being forced to swim from their homes to safety. Others waded through storm waters while some were forced to shelter in place.

An estimated 2,500 people have been displaced from their homes, but that number looks certain to rise.

More than three-quarters of New Zealand’s five million residents live on the North Island, where the brunt of the storm is being felt and where some areas are still inaccessible by road and without power or telecommunications.

The main road between the capital Wellington and the country’s largest city Auckland is closed. New Zealand’s three main mobile phone networks said a total of 455 cell sites were offline.

International and domestic flights have been grounded, with Air New Zealand alone reporting more than 600 flights cancelled and 35,000 customers affected, although airports are gradually reopening.

The military has been deployed to help with evacuations, while Fire and Emergency New Zealand said one firefighter was injured and another disappeared when a house collapsed west of Auckland. A search is under way.