Hard-hit by the quake was the port city of Pisco, 160 miles (260 kilometers) southeast of Lima.

Arriving in Pisco, Minister of Health Carlos Vallejos told Andina television almost 70 percent of the city of 68,000 people was destroyed.

"There aren't any buildings that are in good condition, even the very modern buildings around the central plaza are totally destroyed," Vallejos said.

"There have been more than 200 deaths in this area, and they're still looking for more victims because entire buildings have collapsed."

Hundreds of people were injured in Ica farther south, reported journalist Guillermo Galdos in an interview with ITN. The morgue collapsed, and the International Red Cross has sent body bags to the city, Galdos said. See photos of the devastation »

"The police and military have been sent; they've seen quite a lot of looting," Galdos said.

The two-minute, 8.0-magnitude quake struck Wednesday evening, and strong aftershocks followed, including a 6.0-magnitude temblor on Thursday, according to the U.S. Geological Survey. Watch people coming back to the U.S. from Peru say they're still shaking »

President Alan Garcia declared a state of emergency, including Ica, Chincha and Canete among the other places hardest hit.

Telephone lines were down in a number of cities, and television stations were pleading for viewers to limit cell phone calls so that the lines would be open for emergency use.

Dr. Rubio Luis, director of the Hospital de la Solidaridad in Lima, told Panamericana TV that he had heard many injured people -- rather than seeking medical treatment -- remained at home to protect their valuables from theft.

Luis said most of the injuries included broken bones and fractures. He said he was worried that city water pipes may have broken in the earthquake. If people drink polluted water, he fears an outbreak of intestinal sickness.

The earthquake was more powerful than its initial measurements suggested. The U.S. Geological Survey upgraded it Thursday from 7.9 to 8.0.

When the shaking had stopped, a major highway along the coast was nearly destroyed, said Giorgio Ferrario, head of the Peruvian International Federation of the Red Cross and Red Crescent. Rescuers have been severely hampered by fallen debris, he said.

"It took them seven hours -- seven hours and a half to do normally what is done in two hours and a half because of the road," Ferrario said. "The information gathered from the field is that destruction is extensive."

Towns affected by the quake are old, Ferrario said, and communities are spread out, making communication more difficult.

National civil defense authorities unloaded two planes that flew from Panama with tents and blankets, and Ferrario said he hoped volunteers could begin distributing the supplies Thursday afternoon.

Fernando Calderon, a visiting American who sent photos of the aftermath to CNN's I-Report, said it was chaotic immediately after the earthquake.

"Everybody started crying -- kids, everybody," Calderon said. "Everybody started running toward any empty space. Everybody was afraid the buildings were going to collapse."

The government has closed schools, said Labor Minister Susana Pinilla Cisneros, who announced that Lima's Labor Ministry and other public buildings had sustained damage. See a map of where the quake struck »

The quake struck at 6:41 p.m. (7:41 p.m. ET) and was centered 25 miles (40 kilometers) west-northwest of Chincha Alta and 90 miles (145 kilometers) south-southeast of Lima, according to the U.S. Geological Survey. The epicenter was 25 miles (40 kilometers) below the Earth's surface.

The major quake prompted a tsunami warning, issued by the Pacific Tsunami Warning Center, which was eventually canceled.

A tsunami was generated by the quake, but it was not large enough to be damaging to the Central or South American coast, said Gerard Fryer with the Pacific Tsunami Warning Center.

More than 11 smaller earthquakes occurred in the hours following the original temblor -- most a few miles from its epicenter, but some also in central Peru. Their magnitudes ranged from 5.0 to 6.3.

Peru, and most of the South American Pacific coast, are on the border of two tectonic plates. The South American plate sits beneath the entire continent and extends across the Atlantic about halfway to Africa. The Nazca plate extends across the Pacific along most of the coast.

In October 2005, a 7.6-magnitude earthquake centered in Pakistan killed nearly 75,000 people in Pakistan and India. That quake's epicenter was only six miles (9.6 kilometers) below the Earth's surface. Earthquakes centered closer to the Earth's surface produce stronger shaking and generally can cause more damage than those farther underground. E-mail to a friend

CNN's Steve Tuemmler, Teresa Martini and CNN en Espanol's Willie Lora contributed to this report.