Foreign emergency rescue teams are working to reach areas in and around Indonesia's port city, Padang, which was devastated by a powerful earthquake Wednesday.
The United Nations says the death toll from the 7.6 magnitude quake is at least 1,100. Indonesian officials say at least 770 people have been killed, but they expect the figure to climb as thousands are still believed buried beneath rubble.
Medical teams, search dogs, earth-moving equipment and emergency supplies have been trickling into Padang, the capital of West Sumatra province. Large areas of Padang were destroyed, but rescue operations in and around the city have been moving slowly.
On Friday, U.S. President Barack Obama offered his condolences for the deaths and devastation caused by the earthquake, in a telephone conversation with Indonesia's President Susilo Bambang Yudhoyono.
White House spokesman Robert Gibbs says Mr. Obama also reiterated the U.S. offer to help in the relief operation. President Obama lived in Indonesia for several years as a child.
A Red Cross official in Indonesia, Christine South, says the situation is grave, especially in rural areas outside Padang. She says that in addition to infrastructure damage, some villages may be devastated.
Most of the deaths from the earthquake have been reported in Padang, where at least 500 buildings were toppled by the quake.
Indonesian Health Minister Siti Fadilah Supari has appealed for foreign help to dig out those who are still trapped.
The United States has pledged $300,000 in immediate aid, plus another $3 million for later.
Indonesia is prone to seismic upheaval due to its location on the so-called Pacific Ring of Fire, an arc of volcanos and fault lines encircling the Pacific Basin. In 2004, a 9.1 magnitude earthquake along the same fault line caused a tsunami that killed more than 200,000 people in several countries.
Some information for this report was provided by AFP and AP.