Earthquake-weary Christchurch residents on Tuesday set about cleaning up after a series of powerful tremors, as aftershocks continued to rattle the New Zealand city.

 In what has become an all-too familiar routine for a community hit by three major quakes since last September, emergency crews began work at first light to restore power and mop up flooding from pipes burst in a 6.0-magnitude tremor on Monday.

More than 20,000 homes were without electricity on a bitterly cold night when a 4.7-magnitude shake jolted residents awake at 2:48am (1428 Monday GMT).

"A very rough night in the city," Christchurch mayor Bob Parker told Radio New Zealand.

Businessman Joe Arts said more than 50 aftershocks Monday, the strongest the 6.0 tremor at 2:20pm (0220GMT), were a major setback for Christchurch, which is still recovering from a 6.3 quake in February that killed 181 people.

"It's like we've gone backwards," he told AFP as he surveyed his city centre printing shop, which was damaged but remained open after a 7.0 quake in September but has been closed since the February disaster.

"It's over now, I'll just wait for the insurance payout."

At the beachside suburb of Sumner, the wreckage of a house that tumbled down a hill was cordoned off as work began to stabilise other homes teetering precariously on the edge.

The National Crisis Management Centre said there were no reported fatalities from the latest tremors but at least 10 people were injured.

Schools remained closed across the city and a welfare centre was set up in the suburb of Aranui for people unable to return to their homes.

The worst-hit area was the damaged central city known as the red zone, where up to 50 buildings toppled and which remains off-limits to the public following the earlier earthquakes, accounting for Monday's lack of fatalities.

In an outer suburb a block of shops vacant since the February quake collapsed, as did the historic 134-year-old Timeball Station -- which used to indicate the time to ships -- in the port area of Lyttelton.

Elsewhere in Lyttelton, huge chunks of masonry crashed onto the street as shop facades toppled.

Power company Orion said electricity was initially cut to 54,000 homes but the number had been reduced to 20,000 overnight and services should be restored across the city later on Tuesday.

Prime Minister John Key, who grew up in the city, is expected to inspect the latest damage on Tuesday.

Police urged residents to stay at home and avoid travelling if possible, as repairs were made to damaged infrastructure.

"People have been remarkably calm and rational and we hope this continues, despite the stresses everyone is under," district commander Dave Cliff said.

- AFP/cc