Power was mostly restored to New Zealand's quake-rattled city of Christchurch on Tuesday, following strong aftershocks that brought down new buildings and caused the death of one nursing home resident.

The latest quakes the strongest of which was 6.0 in magnitude, left tens of thousands without electricity Monday, on a winter night when temperatures approached freezing. By Tuesday afternoon, around 7,000 households were still without power. The power company Orion said it was providing generators to fill some of the gap.

Water supplies were also compromised, and Mayor Bob Parker was encouraging people to boil their water.

More than 40 people suffered injuries, most of them minor, in the latest earthquakes. But the Canterbury District Health Board confirmed that a quake caused the death of one elderly resident of a nursing home, according to a spokeswoman who requested anonymity, citing policy. She did not have further details.

Monday's quakes sent bricks crashing down in the cordoned-off city center, where only workers have tread since it was devastated in February. About 200 people were there when the quakes struck Monday, and two were briefly trapped in a church.

The aftershocks worsened the damage to dozens more buildings and caused one of the last buildings standing in downtown to collapse. One house fell off a cliff in the shaking.

On Tuesday, Parker warned residents not to enter houses that have been condemned.

"We can avoid calamities for our people even if we can't our buildings," he said.