Updated

Chilean authorities extended an overnight curfew to midday Tuesday as thousands of troops struggled to contain out-of-control looting and crime in the wake of the devastating earthquake.

Despite the heavy military presence in the badly damaged city of Concepcion, looters burned stores and residents complained of deteriorating security and slow government delivery of food and other basic supplies. Soldiers fired tear gas in efforts to restrict disorder.

SLIDESHOW: Chilean quake devastation

Residents of the city, with a population of 600,000, said they were organizing groups to defend their properties from robbers and looters.

The governor of the region, Jaime Tohá, said that 55 people were arrested on Sunday night for violating the curfew after looters raided almost every market in the city. Some residents rifled through abandoned supermarkets for basic supplies while others took advantage of the crisis to rob banks and empty stores of luxury goods.

The Deputy Interior Minister, Patricio Rosende, said that another 105 people were arrested yesterday for looting and other crimes, and that one person had been shot dead during the night.

"Shots were fired. Police took control of the area," he said, without giving details. Last night the roof of a supermarket in Concepción collapsed when looters set fire to it after police tried to disperse them.

The city’s mayor has said the criminal elements were now becoming more organised and systematic following Saturday morning’s 8.8-magnitude quake that killed at least 795 people, according to local media.

Mayor Jacqueline Van Rysselberghe warned against serious "social tension" in the city. "We need food for the people. We are without supplies, and if we don’t resolve that we are going to have serious security problems during the night," she said. "We are at the end of the month. There are no stocks in the households. But nothing justifies looting, vandalism and theft. We have seen people coming out of supermarkets with plasma screens. If we don’t resolve this problem of food today, we could have a very confrontational situation."

U.S. Secretary of State Hillary Rodham Clinton said she was bringing 20 satellite phones as a first piece of a much larger U.S. aid package. Argentina said it was sending six aircraft loaded with a field hospital, 55 doctors and water treatment plants, and Brazil said it was sending a field hospital and rescue teams. Brazil's president, Luiz Inacio Lula da Silva, visited the capital of Santiago to express his solidarity.

Chilean President Michelle Bachelet said authorities were flying 320 tons of food, water and other basics into the quake zone.

Assessments of damage to Chile's economy were in the early stage. The copper industry was spared, while Concha y Toro, Chile's biggest winemaker, said Monday that the quake has forced it to halt production for at least a week while it assesses damage.

Security was a major concern in Concepcion and other hard-hit towns. Most markets in Concepcion were ransacked by looters and people desperate for food, water, toilet paper, gasoline and other essentials Sunday, prompting authorities to send troops and impose an overnight curfew in the city. The interior ministry extended the Concepcion curfew to run from 8 p.m. Monday to noon Tuesday.

When a small convoy of armored vehicles drove along a downtown street, bystanders applauded, shouting: "Finally! Finally!"

Throughout Talcahuano, stick-wielding residents barricaded streets with tires and rubble to protect their homes in the absence of law enforcement.

Downtown, eight suspected looters kneeled outside a pharmacy, their hands on their heads, as a police officer taunted them.

"Are you praying?" he shouted. "I don't hear you. Pray."

The Times of London and The Associated Press contributed to this report.