New Zealand quake: Christchurch hit by aftershocks
A series of earthquakes has hit the New Zealand city of Christchurch, almost four months after a tremor devastated the area and killed 181 people.
The latest quakes struck just miles from the city, and left about 50,000 people without power.
The most powerful tremor, measured at magnitude 6.0, caused the evacuation of shopping centres, office blocks and Christchurch airport.
The city's mayor Bob Parker warned that more tremors were likely.
"It will be a restless night. It's pretty realistic to expect overnight we will have some more aftershocks," he said.
With temperatures just above freezing overnight, Mr Parker told many Christchurch residents to prepare for a night without power.
"If you don't have power and don't have water at the moment, assume you won't have them overnight," he said.
The BBC's Nick Bryant says the city's quake-weary residents are at their wit's end, and dozens more families have decided to leave for good.
Since the earthquake in February, 50,000 residents have relocated elsewhere in New Zealand and Australia.
"We can't bring up our kids in an atmosphere where they're frightened to go home, to go out to be with their friends," one Christchurch resident told the BBC.
Education officials say many schools will be closed on Tuesday, and the police are warning people to stay off the roads while officials check that they are safe.
Prime Minister John Key said the tremors would not weaken the country's resolve to rebuild the city.
"The people of Christchurch should know that all New Zealanders are thinking of them and will continue to support and stand by them at this very difficult time," he said.
Several buildings collapsed in the latest quakes, and Christchurch Cathedral, badly damaged by February's tremor, lost more of its masonry.
Meanwhile, an inquiry into the collapse of one of the buildings destroyed by the devastating 22 February earthquake opened on Monday.
The inquiry was briefly evacuated during the latest quakes.
About 10,000 houses and nearly 1,000 commercial buildings will have to be demolished as a result of the February quake.
Recovery and reconstruction costs are expected to total at least NZ$15bn ($11bn; £7bn).