In several towns people ran in panic after a false tsunami alert
Strong aftershocks have hit areas devastated by last week's earthquake in central Chile, triggering brief panic.
The tremors of magnitude 5.5 and higher were felt in several cities, including Santiago. They prompted tsunami warnings, but these were later lifted.
Nearly 800 people are known to have died in last Saturday's 8.8 magnitude quake and the tsunami it generated.
Meanwhile, President Michelle Bachelet denied reports there were shortages of food and fuel in the quake-hit areas.
Aid is being distributed in Concepcion and other badly-damaged towns where the army had to quell outbreaks of looting.
The 14,000 troops Mrs Bachelet had sent to the earthquake zone restored order in Concepcion, Chile's second-largest city, after an 18-hour curfew was put in place to prevent looting that broke out.
The curfew was extended from 1800 (2100 GMT) on Tuesday to noon Wednesday in Concepcion and similar curfews have been imposed in six other towns badly affected by the earthquake.
On Wednesday, President Bachelet sought to calm fears that there was not enough food and water in the earthquake zone.
"There is no shortage, there is enough food and therefore we must remain calm," she said.
"There is also enough fuel, there is no risk of shortages."
Dozens of people were arrested in Concepcion on Monday for looting and on Tuesday the mayor of Hualpen appealed for help in a radio interview, saying his town had been taken over by "thugs".
Troops are fanning out to supervise the delivery of food, medicine and water to hundreds of thousands of people in need.
A special air route has been set up to deliver aid from the capital, Santiago, to Concepcion, 430km (270 miles) to the south.
International aid from Chile's neighbours has been arriving as well.
Rescue crews with sniffer dogs have stepped up the search for survivors and in Concepcion, heavy equipment is being used to help move the heaps of rubble.
Officials say 799 people are confirmed to have died but there are reports of many people still missing in the coastal town of Constitucion.
There have been complaints that the number of deaths could have been lower if the government had moved more quickly immediately after the earthquake struck before dawn on Saturday.
An admiral said Chile's navy was partially to blame for the lack of a clear tsunami warning, but said the natural disaster agency should share the blame.
"We were unclear with the information we gave because we were not precise enough to tell the president if the alert was to be maintained or cancelled," said the navy's Admiral Edmundo Gonzalez.
"And this undoubtedly, with the information that the head of the [oceanographic service] gave to the president, undoubtedly stopped the [government natural disaster agency], under instructions from the president, from declaring an alert."
The head of the natural disaster agency, Carmen Fernandez, said an earlier alert would not have helped save lives because there was no system in place to tell people in time.
The tsunami reached across the Pacific, hitting New Zealand and Japan with surges of water a metre (3ft) or more high about 24 hours after the earthquake.
In Chile, about 200km (124 miles) of coastline were swept by the tsunami with waves of up to six metres hitting some towns.
In places the water reached 2km inland, said an emergency official in the Maule region.
About two million Chileans are believed to have been affected by Saturday's earthquake, the seventh most powerful on record and the worst disaster to befall Chile in 50 years.
The epicentre of the quake was 115km north-east of Concepcion and 325km south-west of the capital Santiago.
About 1.5 million homes in Chile have been damaged. Most of the collapsed buildings were of older design - including many historic structures.