Rescuers were left scrambling to reach Kaikoura in the South Island, which had no telecommunications and was isolated by landslips, making it accessible only by helicopter.

Civil defence minister Gerry Brownlee said a clearer picture of the scale of the damage was slowly emerging.

"I think had there been serious injury or suspected further loss of life than we would have heard about it by now," he told Radio New Zealand.

He added: "It looks as though it's the infrastructure that's the biggest problem, although I don't want to take away from the suffering... and terrible fright so many people have had."

Mr Brownlee and John Key, the prime minister, flew over the affected area in a military helicopter.