New Zealand remembers earthquake victims

New Zealand has paused for two minutes of silence to mark the first anniversary of the devastating Christchurch earthquake, which left 185 people dead.

At 12.51pm (11.51pm Irish time), the moment the earthquake hit New Zealand's second largest city, the nation fell quiet to honour the dead.

The 6.3-magnitude earthquake flattened office blocks and toppled buildings onto lunchtime crowds.

About 60,000 people gathered for a solemn memorial at Christchurch's Hagley Park, where families of the victims locked arms and bowed their heads.

185 butterflies were released in a gesture organisers said symbolised departed souls and rebirth.

Ahead of the public memorial, Prime Minister John Key told a separate service for victims' families held near the shattered city centre that the earthquake was "one of our darkest days".

Mr Key said the earthquake "wreaked havoc on an unimaginable scale", changing Christchurch forever.

"It twisted buildings, tore up roads, destroyed homes and shook us to the core," he told the multi-faith service. "Worst of all it stole 185 loved ones from us and injured so many more."

Mr Key recalled visiting Christchurch's Latimer Square in the hours after the earthquake, as fires raged in collapsed buildings, choking dust filled the air, sirens blared and aftershocks continued to rattle the city.

"It was New Zealand, but not a New Zealand I've ever seen before ... the earthquake took everyday life in Canterbury and tossed it on its head, but it could not break the spirit you are famous for," he said.

Mr Key also acknowledged frustration among Christchurch residents at delays to the rebuilding programme amid ongoing aftershocks, including major tremors in June and December that caused further damage.

"We have a long journey ahead of us," he said, reiterating the government's determination to rebuild the South Island city.