Padang, Indonesia - Rescue workers were searching Friday for survivors and bodies under the rubble of collapsed buildings in Indonesia's West Sumatra as the United Nations estimated 1,100 people were killed in the massive earthquake.

Limited heavy machinery hampered the search operation. Many soldiers, police, paramedics and volunteers were searching - often with bare hands - combing the rubble of collapsed buildings for signs of life.

"We're badly in need of additional heavy equipment because there are still many people trapped under tons of collapsed buildings," said Zul Ariman, head of the West Sumatra's search operation.

"We have a limited number of heavy machineries. Moving those equipments from one place to another location is also not an easy work."

Other officials said darkness was another obstacle for rescue workers.

Due to the scattered damage, rescue workers have not even begun to penetrate the piles of rubble at several locations, witnesses said, leaving those trapped to stay longer under ruins.

The Social Ministry late Thursday put casualties at 529 dead and more than 2,100 injured. Officials have said the death toll could rise sharply as thousands of people are reportedly missing and feared trapped under rubble.

The United Nations estimated 1,100 people have died in West Sumatra with the death toll expected to rise.

Fearful of aftershocks, survivors slept outdoors in the dark on mats and plastic sheets for a second straight night as power remained cut off. Officials expected to restore electricity on Friday or Saturday.

Many people were camped at the airport.

Television footage from Padang showed thousands of vehicles queued for hours to get fuel at local petrol stations. Some drivers became angry amid the long waits.

Wednesday's 7.6-magnitude quake displaced thousands of people and damaged key infrastructure, including telecommunications, roads, bridges and water-supply systems.

More paramedics were being dispatched to help local doctors who have been working frantically to treat hundreds of people for broken bones, head injuries and other trauma. Ambulances drove continuously to and from hospitals carrying survivors and bodies found by rescue workers.

Indonesian President Susilo Bambang Yudhoyono, who spent Thursday night in the West Sumatran capital of Padang, pledged to do "everything we can" to help the victims.

Dozens of people were feared buried alive in the collapsed five- storey Ambacang hotel in Padang, popular with surfers and other foreign tourists. It was not immediately known if any foreigners were among the dead.

Health Minister Siti Fadilah Supari said that thousands of people might have been killed in the earthquake with damage that could be worse than the 2006 Yogyakarta quake in Central Java, which killed more than 5,800 people and destroyed or damaged more than 150,000 buildings.

Indonesia, the world's largest archipelago nation, sits on the Pacific "Ring of Fire," the edge of a tectonic plate prone to seismic upheaval.

A major earthquake and subsequent tsunami struck in December 2004, leaving more than 170,000 people dead or missing in Indonesia's Aceh province and 500,000 people homeless.

Geologists have said that Padang, a low-lying city of 900,000 people, risks being swallowed by a tsunami in the event of an earthquake similar in magnitude to the one that triggered the giant 2004 wave.

An earthquake last struck Padang in 2007, killing dozens of people and injuring scores. (dpa)