The quake struck at 1251 local time (2351 GMT) at shallow depth, when the South Island city was at its busiest.

The death toll currently stands at 154, but officials say it could rise as high as 240 as dozens of people are missing.

Frequent aftershocks have been hampering rescue efforts. The cost of the 6.3-magnitude quake is expected to reach US$15billion.

On February 28, the whole country fell silent to mark the moment the deadly earthquake struck seven days ago. Rescuers downed their tools for two minutes before resuming their work.

At a police briefing earlier in the day, Superintendent Dave Cliff said the death toll was likely to climb higher than the previous estimate of 200.

"We need to start considering the figure of around 240 but it is not locked in stone, because we're still getting information in," Mr Cliff said.

Prime Minister John Key has promised a major inquiry, saying there were legitimate questions about why so many buildings had collapsed.

He said there was still a glimmer of hope survivors could be found. However, rescuers have not pulled out anyone alive from the rubble since Wednesday.

The prime minister also announced an initial NZ$120m package of subsidies that will pay the salaries of people who cannot return to work because of the quake damage.