Around 510 people have been confirmed dead and 1,000 injured since the 8.0 magnitude tremor hit on Wednesday, the United Nations said.
Many of the victims in one of the country's worst natural disasters for decades were poor residents of flimsy mud-brick homes.
Thousands of people have been made homeless and forced to sleep outdoors. Survivors have also complained of a lack of medical attention and emergency supplies.
Witnesses said there were no immediate reports of any damage or injuries being caused by the aftershock, centered 145km south of the coastal capital, Lima.
The Peruvian geophysical institute said there had been about 300 aftershocks recorded since the earthquake.
A domestic and international aid effort is under way to help those affected.
"We have been evaluating the material damages and the urgent needs of the population," Luis Gonzales Posada, the head of Peru's congress told RPP radio network on a visit to Pisco. "We have here thousands of people we need to feed."
The Peruvian navy announced it was sending two ships to the devastated region with drinking water and a hospital ship to treat the wounded.
Aid convoy looted
Outside the coastal town of Pisco - the area hardest-hit by the quake - a crowd blocked a road close to an air force base where the relief programme is being co-ordinated.
Local radio reported that truck drivers did not resist as desperate residents looted vehicles carrying food and water.
|Hundreds of coffins are needed in areas |
affected by the earthquake [AFP]
Hours later another mob attempted to raid a convoy of trucks carrying emergency supplies close to the provincial capital of Ica.
President Garcia visited Pisco on Thursday and was besieged by desperate residents.
"Mr. President, we need coffins!" one shouted as Garcia reached a square where 50 bodies were waiting to be identified. Dozens of unidentified bodies are still lying on the streets of the town.
Police in nearby Chincha are searching for more than 600 inmates who fled from a prison after it was destroyed by the quake.
The fugitives include kidnappers, thieves, drug dealers and rapists, General Eduardo Montero, a senior national police commander, said.
The United Nations said it had mobilised almost $1m in aid from several of its agencies, while the Geneva-based International Federation of the Red Cross said it had sent two aeroplanes loaded with relief supplies.
Pope Benedict XVI called for Roman Catholic organisations to provide assistance, as groups such as Firefighters without Borders and Oxfam launched their relief efforts.
George Bush, the US president, offered his condolences and $100,000 in emergency aid, with the possibility of more to come.
The inter-American development bank said it was sending $200,000 in immediate humanitarian assistance.
Colombia is flying 20 tonnes of water, medicine, blankets and other aid, as well as supplying 20 rescue workers.
Brazil said it would send medicine, food and tents "as soon as possible".
The country will hold three days of mourning for those who died.