With minutes left in the Mass, the church's ceiling began to break apart. The shaking lasted for an agonizing two minutes, burying 200 people, according to the town's mayor. Only two stone columns and the church's dome rose from a giant pile of stone, bricks, wood and dust.

One man shouted at the bodies of his wife and two small daughters as they were pulled from the rubble: "Why did you go? Why?"

As dusk fell, Health Minister Carlos Vallejos said finding survivors seemed increasingly unlikely.

Felipe Gutierrez, 82, sat in his pajamas — his only clothing — in front of what was his Pisco home. The quake reduced it to rubble and he, his 74-year-old wife, their two children and three grandchildren sat staring at the ruins, a tangle of adobe, straw and all of their belongings.

"Yesterday we slept on a mattress, and now we'll have to set up a tent, because we have no where to live," he said.

Garcia flew by helicopter to Ica, a city of 120,000 where a quarter of the buildings collapsed, and declared a state of emergency.

Government doctors called off their national strike for higher pay to handle the emergency.

International help includes cash from the United States, United Nations, Red Cross and European Union as well as tents, water, medicine and other supplies. The U.S. Navy hospital ship Comfort, equipped with a staff of 800 and 12 operating rooms, is in Ecuador and could quickly sail to Peru if asked, U.S. officials said.

Sean McCormack, a State Department spokesman, said an American medical team had been on a training mission in the area at the time of the quake, and its members have now split up to and are working with local authorities to assist.

Electricity, water and phone service were down in much of southern Peru. Rescue convoys were slowed by giant cracks and fallen power lines on the Panamerican Highway.

In Chincha, a small town near Pisco only 25 miles from the quake's epicenter, an AP Television News cameraman counted 30 bodies in a hospital patio. The face of one victim was uncovered, her eyes open. The feet of another stuck out from under a blanket.

Scientists said the quake was a "megathrust" — a type of earthquake similar to the catastrophic Indian Ocean temblor in 2004 that generated deadly tsunami waves. "Megathrusts produce the largest earthquakes on the planet," USGS geophysicist Paul Earle said.

In general, magnitude 8 quakes are capable of causing tremendous damage. Quakes of magnitude 2.5 to 3 are the smallest generally felt, and every increase of one number on the magnitude scale means that the quake's magnitude is 10 times as great.

The temblor occurred in one of the most seismically active regions in the world at the boundary where the Nazca and South American tectonic plates meet. The plates are moving together at a rate of 3 inches a year, Earle said.

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Associated Press writers Monte Hayes, Edison Lopez and Leslie Josephs in Lima, Martin Mejia and Mauricio Munoz in Ica, Edith M. Lederer at the United Nations, Alicia Chang in Los Angeles and Sarah DiLorenzo in New York contributed to this report.