Powerful aftershocks have rattled buildings and sent terrified residents fleeing into the streets in the Chilean city of Concepcion.
Fears of of additional damage in the tremors before dawn on Friday led officials to evacuate some patients from the regional hospital.
Patricia Correa, who was overseeing the hospital's emergency ward, said her part of the five-story building was "on the point of collapsing. The walls cracked".
The strongest of the aftershocks was a magnitude 6.6.
"Some chunks of buildings that were already in bad condition fell, but nothing significant," a senior government official in quake-hit Bio Bio region told local radio.
Ban Ki-moon, the UN secretary general, arrived in the capital, Santiago, on Friday, promising support for Chile.
"The Chilean government is asking for international aid and we will give it," he said.
Meanwhile, Michelle Bachelet, the outgoing Chilean president, met with Sebastian Pinera, her successor, and they promised to try to avoid letting the March 11 hand-over of power interrupt aid efforts.
"The new government will have an immense challenge," Bachelet said.
Pinera has even before his inauguration named new governors for the six hardest-hit regions and told them to get to work.
Officials were still struggling to determine the death toll of the magnitude-8.8 quake, as well as the damage to roads, ports and hospitals.
Disaster officials announced they had double-counted at least 271 missing as dead in the hardest-hit part of the country - an error that would drop the official death toll to about 540 if there were no other mistakes.
But interior department officials said that from now on, they would release only the number of dead who had been identified: 279 as of Friday.
Uncertainty to remain
Doubts over the death toll are likely to persist, partly because an undetermined number of victims were washed out to sea in the ensuing tsunamis and some bodies may never be recovered.
"The number of disappeared is very difficult to determine," Patricio Bustos, a government forensics specialist in the city of Talca, said.
"It can take a very long time."
The government said on Friday it had removed Mariano Rojas as head of the Navy's oceanographic service over its failure to issue a tsunami warning for the Pacific immediately after Saturday's quake.
Port captains in several towns issued their own warnings, but a national alert never came, and some say that failure led to deaths.