The death toll rose to 510 on Thursday in the magnitude-8 earthquake that devastated cities of adobe and brick in Peru's southern desert. Survivors wearing blankets walked like ghosts through the ruins. The dust-covered dead were pulled out and laid in rows in the streets, or beneath bloodstained sheets at damaged hospitals and morgues. Doctors struggled to help more than 1,500 injured, including hundreds who waited on cots in the open air, fearing more aftershocks would send the structures crashing down. The center of the destruction was in Peru's southern desert, in the oasis city of Ica and the nearby port of Pisco, about 125 miles (200 kilometers) southeast of the capital, Lima. The United Nations said the death toll was expected to rise beyond the 450 reported by Peru. "It is quite likely that the numbers will continue to go up since the destruction of the houses in this area is quite total," said Assistant Secretary-General Margareta Wahlstrom. Pisco's mayor said at least 200 people were buried in the rubble of a church where they had been attending a service. Some 17 others were killed inside a church in Ica, according to the Canal N cable news station. The historic Senor de Luren church was among several heavily damaged in Ica, where at least 57 bodies were taken to the morgue. Services were packed when the quake struck at 6:40 p.m. Wednesday because Aug. 15 is celebrated by Roman Catholics as the day when the Virgin Mary rose up to heaven. "The dead are scattered by the dozens on the streets," Pisco Mayor Juan Mendoza told Lima radio station CPN, sobbing. "We don't have lights, water, communications. Most houses have fallen. Churches, stores, hotels - everything is destroyed." The earthquake's magnitude - a measure of the energy released at its epicenter - was raised from 7.9 to 8 on Thursday by the US Geological Survey, meaning this quake was capable of tremendous damage. At least 14 aftershocks of magnitude 5 or greater followed, complicating rescue efforts and causing renewed anxiety. President Alan Garcia flew by helicopter to Ica, a city of 120,000 where a quarter of the buildings collapsed, and declared a state of emergency. He said flights were reaching Ica to take in aid and take out the injured. Government doctors called off their national strike for higher pay. "There has been a good international response even without Peru asking for it, and they've been very generous," Garcia said during a stop in Pisco, where so many buildings fell that streets were covered with small mountains of adobe bricks and broken furniture. The help includes several million dollars in cash from the UN, Red Cross, European Union and United States, as well as tents, water, medicine and other supplies. The US Navy Ship Comfort, equipped with a medical staff of 800 and 12 operating rooms, is currently in Ecuador and could quickly sail to Peru if asked, US officials said. In Washington, President George W. Bush offered condolences. One American also died in the quake, according to the State Department. Electricity, water and phone service were down in much of southern Peru. The government rushed police, soldiers and doctors to the area, but traffic was paralyzed by giant cracks and fallen power lines on the Panamerican Highway. Large boulders also blocked Peru's Central Highway to the Andes mountains. Many people said they had seen "lights in the sky," a phenomenon authorities attributed to short circuits at electrical plants where the quake damaged cables and other equipment. In Chincha, a small town near Pisco only 45 kilometers (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 protruded from under a blanket. Hundreds of the injured lay side-by-side on cots on walkways and in gardens outside hospital buildings, kept outside for fear that aftershocks could topple the cracked walls. "Our services are saturated and half of the hospital has collapsed," Dr. Huber Malma said as he single-handedly attended to dozens of people. The quake toppled a wall in Chincha's prison, allowing at least 600 prisoners to flee. Only 29 were recaptured, said national prisons official Manuel Aguilar. Overstretched police and rescue workers in orange uniforms tried to help survivors, who tried to get some sleep in the streets amid collapsed adobe homes. "We're all frightened to return to our houses," Maria Cortez said, staring vacantly at the half of her house that was still standing. The Peruvian Red Cross arrived in Ica and Pisco 7? hours after the initial quake, about three times as long as it would normally have taken because of road damage, Red Cross official Giorgio Ferrario said. In Lima, 95 miles (150 kilometers) from the epicenter, only one death was recorded. But the furious two minutes of shaking prompted thousands to flee into the streets and sleep in public parks. "The earth moved differently this time. It made waves and the earth was like jelly," said Antony Falconi, 27, trying to find a bus to take him home. 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," said USGS geophysicist Paul Earle. The smallest quakes felt by people have magnitudes of 2.5 to 3, and every whole-number increase on the scale a tenfold increase in magnitude _ so a magnitude 8 is quite large indeed. Wednesday's quake caused a tsunami as well, but scientists expected surges of no more than half a meter (1.6 feet) in faraway Japan. 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 (7.5 cms) a year, Earle said. The last time a quake of magnitude 7.0 or larger struck Peru was in September 2005, when a 7.5-magnitude earthquake rocked the country's northern jungle, killing four people. In 2001, a 7.9-magnitude quake struck near the southern Andean city of Arequipa, killing 71.