A powerful 7.8-magnitude earthquake killed two people and caused massive infrastructure damage in New Zealand on Monday, as forecasters warned wild weather could hamper rescue efforts.

The tremor, one of the most powerful ever recorded in the quake-prone South Pacific nation, hit just after midnight near the South Island seaside tourist town of Kaikoura.

It triggered a tsunami alert that sent thousands of people fleeing for higher ground across large parts of the country’s rugged coastline before the threat abated.

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.