The Chilean military is attempting to restore order in the country's second city, Concepcion, amid looting after Saturday's devastating earthquake.
One man was shot and killed and some 160 arrested as troops tried to stop the looting of food and other goods during an overnight curfew.
The death toll from the 8.8-magnitude quake rose to 723 on Monday, with 19 people reported missing.
The United Nations has said it will rush aid deliveries to Chile.
UN spokeswoman Elisabeth Byrs said Chile had requested field hospitals with surgery facilities, mobile bridges, communications equipment, kitchens, and disaster assessment and co-ordination teams.
In coastal towns and villages hit by giant waves after the earthquake, the scale of destruction is becoming clear.
More than 300 bodies were reportedly found in the fishing village of Constitucion alone. The mayor of Constitucion said the town's seafront and centre had been "completely destroyed"
In the port of Talcahuano, more than 20 boats were swept ashore and dumped in the streets by the waves.
Chile's Defence Minister Francisco Vidal has admitted the country's navy made a mistake by not immediately issuing a tsunami warning after the earthquake, a move that could have helped coastal residents flee to higher ground sooner.
But, he added, an alarm sounded by port captains had saved hundreds, if not thousands, of lives.
'Social tension'
In Concepcion, large numbers of police were deployed to enforce an overnight curfew.
Some 160 people were arrested as officers tried to stop people looting stores and homes, and one man was shot dead during disturbances, police said.
Many of Concepcion's 500,000 inhabitants are short of food and have seen their water and electricity supplies cut off.
The army was called in to help the police force deal with looters, some of whom filled shopping trolleys with groceries while others made off with plasma TVs and other electrical appliances.
The government said the overnight curfew imposed in some of the worst-hit areas was largely observed, despite a number of strong aftershocks.
Meanwhile, rescuers with heat detectors are hunting for dozens of people believed to be trapped in an apartment block toppled by the quake.
The city's Mayor, Jacqueline van Rysselberghe, has warned there is the potential for severe "social tension".
She said: "We need food for the population. We are without supplies, and if we don't resolve that we are going to have serious security problems."
Regional military commander Guillermo Ramirez issued a warning to would-be looters.
"I would advise criminals not to mess with the armed forces. Our response will be severe, but within the context of the law," he said.
'Giant effort'
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.
President Michelle Bachelet, due to hand power to President-elect Sebastian Pinera on 11 March, said the air force was to begin flying in food and vital aid to badly-hit areas, some of which have been cut off by the quake.
"We face a catastrophe of such unthinkable magnitude that it will require a giant effort," she said.
Chile did not initially request foreign assistance, but Ms Bachelet has subsequently said some offers of aid would be accepted.
She said Chile needed field hospitals, temporary bridges, water purification plants, damage assessment experts and rescuers to relieve those already working to find survivors.
Emergency aid
The epicentre of the quake was 115km (70 miles) north-east of Concepcion and 325km (202 miles) 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.
About 90% of the historic centre of the town of Curico was destroyed. Many roads and bridges across the affected area were damaged or destroyed.
One US risk assessor, Eqecat, has put the cost of repairing the damage at between $15bn and $30bn (£9.8bn-£19.6bn) or 10-20% of gross domestic product.
US Secretary of State Hillary Clinton would visit Santiago on Tuesday and meet Ms Bachelet and Mr Pinera, officials said.
The European Union has pledged 3m euros ($4m; £2.7m) in emergency aid for Chile. Japan said it was providing an emergency grant of $3m, as well as sending tents, generators, water cleaners and other emergency gear, while China has pledged $1m.
