CONSTITUCION, Chile — Looting spread in earthquake-leveled parts of Chile on Monday even as army troops deployed in armored vehicles and on horseback to restore order and protect shipments of food and water. Scores of people were arrested for violating an overnight curfew.

With the death toll creeping higher, Chile continued to reel from Saturday’s massive magnitude 8.8 quake, one of the strongest on record. At least 723 people were killed, the government said, and many remained missing.

Numerous oceanfront towns, like Lloca, Dichato and Constitucion, were devastated first by the quake and then, minutes later, by tsunamis, a kind of seismic coup de grace. Little or no help had reached these sites, residents said.

“”We need food! We need water!”” said a beleagueredCesar Arrellano, a municipal comptroller in Constitucion who received unrelenting reports of damage, death and the desperate need for help.

Chile’s second largest city, Concepcion, seemed to be suffering the brunt of post-disaster chaos. Looters raided a firehouse in search for water and gasoline that are in short supply; others later torched a shopping center.

Concepcion MayorJacqueline Van Rysselberghesaid looters were moving in organized packs and attacking firefighters and city workers attempting to distribute water.

“”Our firefighters, our personnel, don’t want to keep doing this work in these circumstances,”” she said. “”If a bigger contingent (of soldiers) isn’t sent here quickly the people will begin to take the law into their own hands.””

Fire raged in a downtown Concepcion shopping mall. A radio reporter said she saw people in a vehicle toss a Molotov cocktail into the collection of stores just before the fire erupted. Firefighters could do nothing: They had no water. The building, looted earlier in the day, was collapsing under the flames.

PresidentMichelle Bacheletimposed emergency decrees, including putting the army in charge of hard-hit areas, measures not taken in more than 20 years.

The government promised to distribute food, water and other essential supplies on Monday in Concepcion and other communities. But aid seemed to trickle in, slowed by mangled roads, collapsed bridges and the lack of electricity. A small plane bringing aid to Concepcion crashed Monday, killing all six people on board.

Bachelet called on power companies to restore energy to hospitals and clinics and urged local authorities to quickly identify and bury bodies. In Constitucion, caskets were stacked in the town gym that had been converted into a morgue.

Bachelet declared a 30-day state of emergency for the coastal states ofBio Bioand Maule, sent in the army and slapped an overnight curfew on major cities in the region. It was the first time a government has taken action to suspend some civil rights since democracy was restored to Chile 20 years ago. Using the army for public security is still a sensitive subject in Chile, a country that endured nearly two decades of military dictatorship before the 1990 ouster of Gen.Augusto Pinochet’sregime.

The possibility of a “”social explosion”” quickly emerged as the government’s “”worst fear,”” the leading Chilean newspaper El Mercurio reported, noting the emergency decree was agreed to only after intense debate because of its potential symbolism.

“”Coordination between civilian and military authorities is functioning correctly,”” government spokeswoman Pilar Armanet said. “”We are attempting to normalize basic services, with the difficulties that implies.””

In a sign of the government’s alarm over deteriorating conditions, Defense MinisterFrancisco Vidalannounced that the curfew imposed for Concepcion and its surroundings would be lengthened to begin Monday night at 8 and extend to noon Tuesday.

Deputy Interior MinisterPatricio Rosendesought to calm the public amid reports of roving mobs and vigilantes in suburbs around Concepcion.

“”Undoubtedly we can’t have the military on every corner, but public order is in the hands of the armed forces and you must trust in that,”” he said.

In Concepcion, rescue efforts centered on a 15-story apartment building that collapsed onto its side. Rescue workers equipped with search dogs and architectural blueprints sliced through concrete and punched triangular holes into the side of the building in hopes of finding survivors.

On Sunday, eight bodies and about two dozen survivors were pulled out but many people were believed trapped. Early Monday, fire brigade commanderJuan Carlos Subercaseauxreported signs of life on what had been the building’s sixth floor.

“”We heard knocking and some glass being broken,”” he told reporters at the site. By afternoon, another body had been recovered and rescuers continued the search for survivors.

In Santiago, the capital, life crept slowly back to normal Monday, with many people driving to work but also with long lines at supermarkets and gasoline stations. The start of school after the southern hemisphere’s summer vacation was postponed until next week.

Slow to ask for help, Bachelet has said she would welcome international aid. The United Nations said Monday it would rush deliveries, and Argentina announced it was sending a field hospital and water treatment plants.

In Washington, U.S. officials said Monday that Chile has made modest requests of the United States so far, leaving it unclear whether the administration would mount a major effort for the earthquake-struck country, as it has for Haiti and others.

Philip J. Crowley, the State Department’s chief spokesman, said the United States has so far been asked to contribute a field hospital, communications equipment and water filtration equipment. U.S. Secretary of StateHillary Rodham Clinton, who will arrive in Santiago Tuesday as part of a five-nation Latin America tour, will bring satellite equipment.

Crowley said the United States “”will stand ready to support them in any way.”” But he said the Chileans are well-prepared and are assessing how much outside help they need.

The United States has not formed a task force to deal with the emergency, as it did quickly with the earthquake in Haiti, Crowley said. American search and rescue teams from Los Angeles and Fairfax County, Va., are on standby, but haven’t been asked to help, he said.

U.S. officials said they sent the Chilean government a 10-page “”grocery list”” of available items, services and workers, including American cardiologists, orthopedists and anesthesiologists.

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(McDonnell reported from Constitucion, Chile, and Wilkinson reported from Mexico City. Times staff writerPaul Richterin Washington and special correspondentClaudia Lagosin Santiago contributed to this report.)