Government officials in Iran say about 20,000 people have been killed and 30,000 injured in Friday's earthquake, which destroyed much of the historic southeastern city of Bam.
Iranian officials are describing the devastation of Friday's earthquake as an unbelievable human disaster.
About 80,000 people live in or near Bam, and Iranian officials say 70 percent of the residential complexes in the city were destroyed.
The quake, which struck early Friday morning, had a magnitude of 6.5, according to U.S. scientists. Several aftershocks, including one that registered a magnitude of 5.3, have since jolted the area.
The city's electricity, water and communications lines have been cut.
In near freezing temperatures, several thousand residents were forced to sleep outside Friday night.
Early Saturday morning, residents and rescue workers were continuing to dig through rubble with shovels and their bare hands, trying to locate possible survivors.
With two of the city's hospitals destroyed, dozens of military planes have reportedly been mobilized to evacuate the injured to medical facilities in Tehran and other cities.
Many residents were seen sitting next to the blanket-wrapped corpses of their loved ones, while others were carrying bodies to local grave sites.
The government has made an urgent appeal to all nations for assistance. President Mohammad Khatami, who declared three days of national mourning for the victims, said the disaster is too huge for Iran to meet all the needs.
The United Nations is mobilizing aid, including blankets, tents, medical supplies and food. Many nations in Europe and Asia, as well as the United States are offering assistance.
With major fault lines running through Iran, the country frequently experiences earthquakes. In 1990, an earthquake struck northwestern Iran, killing tens of thousands of people.