An earthquake with a magnitude of 7.4 struck central New Zealand just after midnight (1202 Malta Sunday), the U.S. Geological Survey said, knocking out power in some areas and sending people into the streets of the capital Wellington.
New Zealand's Civil Defence issued a tsunami warning, advising residents on the South Island's east coast to seek higher ground.
The quake was 91 km (57 miles) north-northeast of Christchurch, the biggest city on New Zealand's South Island. A 6.3 quake there in February 2011 killed 185 people and caused widespread damage.
The tremor, which was measured by New Zealand's Geonet at magnitude 6.6, was felt throughout most of New Zealand. Civil Defence said it was too early to assess the damage or whether there had been any injuries or deaths.
"The whole house rolled like a serpent and some things smashed, the power went out," a woman who gave her name as Elizabeth told Radio New Zealand from her home in Takaka, near the top of the South Island.