Emergency workers are struggling to deal with the aftermath of a devastating earthquake in Peru that has left hundreds of people dead.
Damaged roads are hampering rescuers trying to reach Pisco, Ica, and other rural towns south-west of the capital.
At least 437 people died and many more were injured, officials say.
The UN's Margareta Wahlstrom said power and communications were down and that 80% of houses in some areas had been destroyed because of poor construction.
Ms Wahlstrom, UN deputy emergency relief co-ordinator, said that the death toll was likely to rise as the destruction of buildings in the area was "quite total".
She said almost $1m (£500,000) had already been pledged by several UN agencies to help the quake victims.
The 8.0-magnitude earthquake struck on Wednesday evening at 1841 (2341 GMT), just off the coast of Peru.
The province of Ica was the most damaged, but even in Lima, 150km (95 miles) from the epicentre, people stood trembling on the streets as buildings around them shook.
In the latest developments:
Pisco's mayor says 200 people are buried in the rubble of a church which collapsed during massIn Chincha, about 200 people wait outside a badly damaged hospital, fearing it might collapse
- Severe aftershocks continue into Thursday morning, the strongest of which measures 6.3
Juan Mendoza, mayor of Pisco, told a radio station that "the dead are scattered by the dozens on the streets".
He estimated that 70% of his coastal city was in ruins.
"We don't have lights, water, communications. Most houses have fallen, churches, stores, hotels, everything is destroyed," he said.
President Alan Garcia quickly announced a state of emergency and sent cabinet ministers to the region.
Health workers abandoned an industrial strike to attend to casualties, and rescue teams were despatched from other parts of the country.
However, the damage caused by the quake hampered the emergency effort.
Giorgio Ferrario, head of Peru's Red Cross, said it had taken workers seven-and-a-half hours to get to the province of Ica, rather than the usual two.
He said he expected the official death toll to increase as daylight enabled workers to speed up their search for victims.
In the city of Ica, people sifted through the rubble of the Senor de Luren church, which collapsed during mass.
In Imperial, a town south of Lima, "about 80% of the adobe houses have fallen," Mayor Richard Yactayo told Reuters news agency.
Amid the bitter cold of winter, Imperial's survivors lit fires in their ruined homes to keep themselves warm.
Sense of relief
Hospitals were reported to be overwhelmed by the number of casualties. The floors of the hospital in Chincha were described as covered with dead bodies.
Offers of assistance, whether in the form of rescue experts or relief supplies, came from Spain, France, Ecuador and Bolivia.
President Garcia thanked God that the earthquake had not caused "a catastrophe with an immense number of victims".
In 1970, a 7.9-magnitude earthquake high in the Peruvian Andes triggered a landslide that buried the town of Yungay and killed 66,000 people.
In Lima's poorer suburbs and shanty towns, news of the damage is still coming in, reports the BBC's Dan Collyns.
However, he says the feeling in the city, where one third of the population lives, is that it may have narrowly avoided a major disaster.